It was a close-run thing. The law was passed 49 votes to 44.
Sex between consenting females was not illegal, but many lesbians suffered the same social discrimination as gay men and were staunch supporters of reform.
The Homosexual Law Reform Act amended the Crimes Act 1961 by removing criminal sanctions against consensual homosexual conduct between adult males.
The campaign to reform the law moved beyond the gay community to wider issues of human rights and discrimination.
Extreme viewpoints ensured a lengthy and revealing debate, sparked violent demonstrations and angry rallies. Views ranged from enabling gays and lesbians to be out and about, to the New Zealand family crumbling and Aids spreading through the community.
Nineteen years later, the Civil Union Act came into force, establishing civil unions for same-sex and opposite-sex couples.
In 2013, the Marriage Amendment Act allowed same-sex couples to legally marry.
That last bill was proposed by Louisa Wall more than a quarter of a century after another Labour MP, Fran Wilde, introduced the original bill.
Ricardo Simich, editor of the Herald on Sunday's Spy, PR consultant and event organiser
Dinner-table discussions in the Simich household were disturbing for a pubescent Ricardo Simich.
The proposed law change divided Kiwis at a time when the Aids toll was growing apace. HIV (human immunodeficiency virus) was adopted as the name of the deadly retrovirus and the year before, the disease had claimed Hollywood actor Rock Hudson.
Simich's household was fairly typical. His father and brother loved rugby and were dead against Fran Wilde's bill.
His father, Clem, was a faithful National Party member who would become an MP and Cabinet minister.
"I was just hitting puberty, the age where you become aware of your sexuality," says Simich. "It was not great. At family meals they were vehemently opposed to it."
Nobody in the family had met a gay person save for his mother, Ann, during her days as a model. "I just gulped at the dinner table and was like, shit, there might be a problem here. I just wanted to curl up into a ball under the dinner table."
Home from school ill, he listened to talkback radio with growing horror. "There wasn't a single positive person ringing in, it was like we should all burn in hell. It wasn't the best time to come of age."
Back then, with the Aids epidemic, if you were gay or effeminate and you sneezed, there were people who thought they were going to catch something off you, says Simich.
He told his family he was gay a couple of years later and says his father and brother embraced him immediately. "They became my champions."
His father was not an MP back then, but later was the only male National MP to vote in favour of civil unions. Simich jnr was aware of the party lobbying that went on and understands how difficult that would have been.
Simich snr always said he voted for change because it was right, rather than because of his son. "He always said it was about other people, not me, but I knew deep down. I was very proud of him."
For Simich snr, it was about human rights. "Homosexual people have been discriminated against forever and this bill goes some way to redressing it," he said at the time.
Simich says his father is "quite bewildered" that he had previously had those strong [opposing] views and I think the family is grateful to me for teaching them something different."
The change during his adult life has been phenomenal, says Simich. "I can't believe that 30 years ago I was an illegal human being. I never, because of that bill, had to worry about being arrested."
"The best advice dad ever gave me was, just because you are different, get on with life as normal because that shouldn't define you."
Lynda Topp, legendary twin
The Topp twins were among many women who campaigned and tonight they will welcome guests on the red carpet at a gala dinner at SkyCity to celebrate the anniversary.
A lot of lesbian women realised it was difficult for gay men to demonstrate because the law deemed them criminals, says Topp. She and Jools performed at rallies. "It was an injustice. We put our hands up and said we were going to help. The rally that sticks out is the one in Wellington with Norm Jones' 'get back in the sewers' speech."
"We grew up rurally but we never had any stereotypes put on us by our parents. We also felt we were supported by our mum and dad in whatever decisions we made in life. It didn't matter whether you were a girl or boy at home, you still had to milk the cows, feed them out and all that stuff.
"One thing our mother said to us when we were little was, 'you can dislike things but you must never hate. Another was that things should be fair and equal for everybody."
As performers the Topps had a public voice. "We'd write a song about everything we stood up for. We'd written a song called Paradise, which was about being lesbians, Untouchable Girls and all that sort of stuff."
Though it wasn't a legal issue for women, Topp says, it could have gone the other way and sex acts between women could have been criminalised.
"The great thing that came out for the public of New Zealand was that they saw hate and abuse from the anti-homosexual people and they saw the gay and lesbian community having fabulous parties and celebrating their love for one another."
Jones' speech, which was replayed on television, was pivotal. "They lost it as much as we won it," says Topp, "and now look, we all get married."
She and Jools came out 40 years ago aged 18. "We didn't really talk about it, we just knew. We saw some lesbians in Christchurch and we thought, 'we're just like them'. And the next day we decided we must be, so, yeah we were lesbians."
Not that the whole world was ready to hear it. They happily told reporters during that tour but many newspapers chose not to print the word lesbian. The next year, she says, some social change must have happened because wherever they went they seemed to be billed as "the lesbian Topp twins".
"The classic thing is people get famous and then they have to come out and that is scary. Jools and I came out and then got famous. I think that was the most important thing for us. We were treated all right from the word go. New Zealanders like people who are honest and truthful."
Topp saves the last word for Wilde and Wall, two women who crucially, bravely, "stepped up to the plate".
Peter Gordon, master chef, ONZM
It didn't occur to Peter Gordon that it was illegal to be gay until it wasn't. He was getting on with life, cooking, clubbing. He moved to Melbourne in 1981, travelled through Asia and turned up in Wellington where he set up The Sugar Club late in 1986, after the law change.
His life was relatively untouched by sexual politics.
"I was a gay man in Wellington going dancing at Clare's nightclub, having lots of laughs and fun, living in Karaka Bay, riding a motorbike and thinking life's pretty good.
"I think I was a bit oblivious to what had gone on but I have benefited hugely from the work done by those who went before.
"I think I've known I was gay from a very early age and I have three lesbian sisters."
He finds it hard to understand that being gay is a big issue for some people and is bemused by how vehement some were in their opposition, that the likes of the Salvation Army - which four years ago formally apologised for the hardline position the church took - was so severe and that even Amnesty International would support prisoners of conscience but not gay men or women.
"For me it's like, what's the big deal, we are just normal people, just leave us alone," says Gordon from London. "I'm not so naive as not to know it is a big deal for some but it drives me nuts."
Whanganui-born Gordon came out to his parents in his 20s. He didn't see the need to any earlier. "I had no dramas and didn't feel I had to justify myself. Mum's been amazing, Dad's been fantastic, bless them. There was never a sense of drama or guilt, though it wouldn't have been easy for them."
Gordon has always been matter of fact about his sexual orientation and in 2005, was named as one of the 100 most influential gay and lesbian people in Britain.
He is proud that New Zealand is one of only four Commonwealth countries where same-sex marriage is legal and notes that some have the death penalty for sodomy.
"I thought Australia was such a gay country and it hasn't allowed gay marriages to happen.
"To think New Zealand is such a little country, and there was such opposition and yet commonsense and non-critical judgement of others prevailed. Thirty years - well done Kiwis!"
Blyth Tait, equestrian and Olympian
The four-time Olympian doesn't recall encountering prejudice growing up in New Zealand, which he left in 1989 to pursue a career as an equestrian in the United Kingdom.
"Growing up, and since, I've always thought New Zealand a fairly tolerant place. I've certainly not encountered any significant issues in the pursuit of my sport."
Tait, 55, says he's always been well supported by teammates, sponsors and New Zealand sports management. It was accepted that the relevant factors in his sport were performance and team compatibility.
Aged 25 at the time, he says he was as openly gay as he felt he needed or wanted to be.
"It wasn't a huge deal as far as developing my career was concerned. So I didn't come flying out. Once I was more confident in myself and things got easier I wanted to be true to myself and to those around me. I guess without the reform that wouldn't have been possible.
"I entered my long-term relationship at the end of the 80s and have been in the same relationship for over 25 years. Maybe things would have been different.
"[The reforms] paved the way for me to lead my life and I've been happy at what I've done and have been well supported by those around me. I have never encountered any major negativity from New Zealand in any shape or form.
"I'm very appreciative of other more political people who have worked hard. I am very aware there have been those people and I think New Zealanders are very forward-thinking people."
He thinks it is consequently easier for young gay people to be open today. "Back then it was more difficult, therefore you wanted to remain a bit more private. My parents have been fantastic and I find it difficult to understand the older generation who aren't."