The Footsie index of 100 leading blue-chip stocks is off 28.9 points following an hour's trading in London to stand at 5633.
Performance has been damaged by sharp falls in the US overnight, where the Dow Jones index dived by nearly 1% as traders showed nerves ahead of the Federal Reserve's interest rate decision tomorrow.
Share dealing in London has also been hit by a statement from French IT group Cap Gemini that it is lowering its sales forecast. Computer services group Logica is down 29¾p at 875¼p in response, while CMG has fallen by 13½p to 290p.
Other tech shares on the way down include software group Misys, off 9p at 479p; Dimension Data, down 5p at 290p; and ARM Holdings, 2¾p lower at 256p.
Telecoms are also under pressure, with BT off 8p at 416¼p; Colt Telecom down 20p at 440p; Energis 8½p lighter at 173p; and Telewest Communications off 30 at 84p. Vodafone is also on the slide, 2¼p down at 147½p.
Among the smaller stocks, Carpetright has gained 16p to 616p after reporting a 5.9% jump in sales and saying that pre-tax profits have soared by 21.9% to £44.6 million.
Housebuilder Berkeley has also jumped after traders gave the thumbs up to the group's figures. Its share price is up 18½p to 767½p.
But Claims Direct is down 2½p to 12p after saying it has received a management buy-out approach, which indicated a cash price of 10p a share.