The NZX-50 rose nearly 15 points before lunch yesterday, only to slump badly through the afternoon and end down 10 points on Friday's closing level before the holiday weekend.
The index is now at its lowest for over a month.
It gained in early trading - despite falling stock prices in the United States where weak data were supporting a bearish outlook for the economy - and late in the morning had clawed back most of the 11.1 points lost on Friday.
But at the end of the day, it had dropped 9.15 more points (0.26 per cent) to 3505.61, on a volume of 34 million shares, valued at nearly $92 million. Total NZX trading amounted to 40.7 million shares valued at $97 million. There were 47 rises and 69 falls among the 111 stocks traded.
Freightways rose 9c to $3.35, but Mainfreight fell again, by 6c, to $9.82.
Contact Energy added 5c early but finished the day down 4c at $5.81, and Fletcher Building similarly gained 3c only to finish down 4c at $8.83.
Telecom fell 2.5c to $2.30, with over 11 million shares trading at a value of $26.4 million.
TrustPower was down 5c to $7.40, and Cavalier Corp fell 3c in early trading and finished the day down 9c at $3.75. Sky TV lifted 4c to $5.72 early, but finished down 1c at $5.67.
Some stocks held on to part of their gains: Ryman Healthcare was up 7c early and finished up 3c at $2.74, SkyCity was initially up 3c and finished up 2c at $3.60, while Nuplex gained 3c at first, but finished on par at $3.10.
Across the Tasman, the Australian sharemarket closed flat, regaining earlier lost ground, after the central bank kept interest rates on hold.
The S&P/ASX200 index was down 2.8 points, or 0.06 per cent, at 4566.3, while the broader All Ords was down 7.6 points, or 0.16 per cent, at 4641.1.
On the ASX 24, the June share price index futures contract was down three points at 4566, with 33,368 contracts traded.
In the US, stocks have been battered in the past five weeks on a number of disappointing reports, culminating in data which showed employers added a meagre 54,000 jobs last month and the unemployment rate rose to 9.1 per cent.
The Dow Jones industrial average dropped 0.5 per cent to 12,090.11, the Standard & Poor's 500 Index fell 1.1 per cent to 1286.17, and the Nasdaq Composite Index lost 1.1 per cent to 2702.56.