With five months until the 2013 Vibram Tarawera Ultramarathon the 400 starting spots have already been snapped up.
But those keen to enter the mainly off-road run from Rotorua to Kawerau needn't panic - a waiting list has started.
The 5th annual event takes place on March 16 and consists of either a 100km, 85km or 60km race, either as a solo athlete or a relay team.
Race director Paul Charteris said about 10 per cent of original entrants usually pulled out before the race date, for various reasons.
"A lot on the wait list should get in, but it might get to more than 50 people long," he said, adding there were already 14 on the list.
Charteris said he usually got most of the entries around February, but the race's growing popularity meant people had got in early this time.
"I had 50 entries in the last week after I put the word out spots were going fast. Those sitting on the fence have jumped in.
"Now I know exactly how many runners to plan for, we can organise things."
Charteris said he would like to slightly extend the limit, set four years ago, but that was up to the Department of Conservation and the Lake Okataina Scenic Reserve board.
"If this is an experience people really want to have, to deny them would be a shame."
This year 337 athletes took part, including world class ultrarunners Anton Krupicka (who only ran in the relay because of injury), Vajin Armstrong and eventual winner Australian Mick Donges.
International media attention and word of mouth within the ultrarunning community has attracted entries from 13 countries for next year, including a record 53 from Australia.
Charteris said the field will be the strongest ever, although most of the elite runners would wait until closer to the time before confirming their entries.
"Timothy Olson from Oregon won the most prestigious 100-mile (161km) race in the US this year and set a course record, so he's in good shape. It's the first time we've had the leading US runner.
"Anton [Krupicka] had indicated he will come back. He was really impressed with the quality of the New Zealand runners [this year] and was keen to have a go and compete against them."
Charteris said top Rotorua marathoner Sarah Biss had entered the 100km, so it would be interesting to see how she measured up in the unfamiliar ultradistance.
He said 230 of the 400 entries were for the big one - the 100km.
"It's easily the most popular distance. You offer up that challenge, they take it."
The 100km course record is 8h 33m, set by Sam Wreford in 2011. Charteris said the 2013 event will be "easily the biggest 100km race in New Zealand's history" and he will need more than 100 volunteers to help with aid stations, marshalling and mountain bike patrols.
It's a big job to organise but Charteris reckons it's well worth it, and not just for the athletes.
"It's worth it to Rotorua, it's bringing in a fair bit of money."
For details or to join the waiting list go to www.taraweraultra.co.nz.