At 10.25am (AEST), the benchmark S&P/ASX200 index was down 24.5 points, or 0.53 per cent, at 4571.6 while the broader All Ordinaries was down 20.9 points, or 0.45 per cent, to 4575.4.
RBS Morgans senior equity advisor Tony Russell said the market was down as investors consolidated from last week's gains.
"There is a bit of profit taking now the base of the reporting season has passed and following the lead from the US,'' he said.
"Investors are waiting for further economic indicators to see whether the economic recovery is still on its way, or if it has slowed or quickened.''
Most sectors opened weaker, particularly the financials.
ANZ Banking Group was down 28 cents to $22.40, NAB had lost 41 cents to $28.63, Westpac was off 29 cents to $24.23 and Commonwealth Bank was 59 cents lower at $47.01.
Sydney Gold miners were stronger as the price of the precious metal stayed above the $1000-mark.
Lihir was up 2.98 per cent, at $3.11, Newcrest had added 2.61 per cent to $35.05 and Newmont was 1.48 per cent at $5.48.
At 10.35am the spot price of gold in Sydney was $US1002.90 per fine ounce, up $US3.92 on Friday's closing price of $US998.98.
The major miners were lower however.
BHP Billiton was down 16 cents to $38.14 and Rio Tinto was off 62 cents to $58.61.
US stocks fell on Friday amid profit taking after a five-day rally.
The Dow Jones Industrial Average closed down 22.07 points, or 0.23 per cent, at 9605.41, the tech-heavy Nasdaq composite was down 3.12 points, or 0.15 per cent, to 2080.9 and the broad-market Standard & Poor's 500 index shed 1.41 points, or 0.14 per cent, to 1042.73.
On the Sydney Futures Exchange, the September share price index contract was 30 points lower at 4568 on a volume of 25,587 contracts.
Resources push shares lower at noonStocks tumble amid investors’ worries
