While its rival, IDC, still ranks HP in the lead, but by less than half a percentage point, both studies indicate that HP is starting to lose control of the market.
Worldwide shipments of personal computers fell over eight percent last quarter. This is because retailers and vendors are ridding themselves of older inventory ahead of the launch of Microsoft's Windows 8 and a slowing economy.
Both Gartner and IDC say that Lenovo, Acer and other Asian PC makers are giving HP and Dell a good kicking.
Lenovo's has been doing well thanks to a combination of aggressive pricing, overseas acquisitions and because it is taking advantage of a fast-growing Chinese market.
Lenovo bought its way into the PC market by buying IBM's personal computer division in 2005. Gartner said that it has grown its market share to 15.7 percent, shipping an estimated 13.77 million units during the quarter, up nearly 10 percent from last year
HP's global PC share stood at 15.5 percent after shipping 13.55 million units. This is down 16.4 percent from a year ago. HP has been the top PC vendor position since 2006.
IDC said HP was still number one with 15.9 percent market share and Lenovo coming a close second with 15.7 percent share.
HP insisted to Reuters that the figures from IDC were right because it measured the entire market.