Handspring, which licenses the Palm operating system, has thrown down the guantlet to its rival, ending February with 28 pecent of the US handheld market.
Handspring's result was up from 26 percent the month before. Palm accounted for 59 percent of the market in February, down from 61 percent in January.
Sony, which also uses the Palm OS, controlled 2 percent of the market last month.
Altogether, handhelds that use the Palm OS accounted for 89 percent of the US retail market in February.
Meanwhile, the companies that license Microsoft's Pocket PC operating system held steady last month with a combined 9 percent of the market.
Hewlett-Packard had 4 percent market share; Compaq Computer had 3 percent; and Casio had 2 percent.
All other handheld makers made up the remaining 2 percent.
Pocket PC-based devices are doing better overseas, gaining ground on Palm in Europe.
A recent study by the England-based market researcher Context Integration, showed Palm's European market share had dipped from 59 percent in January 2000 to 55 percent in December.
By contrast, Hewlett-Packard and Compaq, the two largest manufacturers of Pocket PC devices, combined for 31 percent of the European market at year's end, up from 18 percent at the start of 2000.
But it wasn't all good news for Handspring. Samuel May, an analyst at US Bancorp Piper Jaffray, downgraded the company this week from "strong buy" to "buy" on concerns that a slowdown in corporate purchasing could impact the company's revenue.
Handheld computer manufacturers have been engaging in a fierce battle to gain more market share and compete with better products.
On Monday, Palm unveiled two new handheld computers with slimmer bodies and a postage stamp-sized expansion slot. Handspring last week introduced its slimmed-down Visor Edge.
Hewlett-Packard plans to introduce a cheaper color version of its Jornada handheld.
