Workstation shipments totalled 346,846 units in the quarter, down from 417,276 during the same period in 2000, according to the research company.
Dell and IBM were exceptions to the gloomy news. Dell topped worldwide workstation shipments, with 115,800 units - a rise of 24% compared with the same period last year.
IBM saw its workstation unit sales grow by 10% to 46,050 for the quarter, pulling ahead of Hewlett-Packard to fourth place.
Sun Microsystems suffered a slide of nearly 35% in sales, but still took second place at 62,306 units shipped.
The third-place manufacturer was Compaq, whose 50,650 units shipped marked a drop of 16% from last year's third quarter.
HP, at fifth place, took the biggest blow of the group. The company shipped 37,280 units - 47% fewer than last year.
However, Dataquest said there are signs of a recovery in the sector. Workstation sales may show positive growth in the fourth quarter. Many corporate buyers postponed buying hardware during the first half of 2001, but these purchases will have to be made soon, said Dataquest.
The US military campaign in Afghanistan could further boost shipments to government, defence and biotechnology buyers. The 11 September terrorist attack on the World Trade Centre has resulted in a slight increase in workstation purchases by companies that lost offices in the disaster, Dataquest said.