Google's Android operating system passed Research in Motion's Blackberry platform to capture the top U.S. smartphone slot with 31.2 percent market share through January, said comScore.
While Android gained almost 3 percent share from comScore's December count, RIM's Blackberry fell to 30.4 percent share from 31.6 percent.
The statistics underline a dismal holiday selling season and start to 2011 for RIM, which has steadily bled market share to lose over 5 percent share since October, when the researcher counted it at 35.8 percent.
Update: Apple's iOS, which appeared poised to challenge RIM's mantle before Android stormed the charts to take over at No. 1, accounted for 24.7 percent share, up only .01 percent from the prior period.
The company shipped 16.24 million iPads through the holiday quarter and has spent a lot of time the last few months revving up its iPad 2 tablet, which launches March 11.
At RIM's current rate of decline, Apple, which CEO Steve Jobs said last week has sold more than 100 million iPhones since 2007, could top RIM by the time it launches its iPhone 5 this summer. The iPhone 5 is expected to be fitted with near field communication technology to enable mobile payments.
While RIM fades, Microsoft Windows Phone 7 continues to fail to make an impression in the smartphone market. ComScore said Windows accounted for 8 percent market share, down from 8.4 percent in December, 9 percent from November and 9.7 percent through October.
Android's rise on the back of its 100-plus handsets and Apple's continued success with its steadily improving iPhone stem from solid hardware and cutting-edge software functionality and applications. RIM has lost its magic, and Microsoft can't seem to find any-which is why its $1 billion partnership with Nokia is so important.
RIM is suffering from both a branding and development crisis.
There is hope yet for RIM and Microsoft, as people are still snapping up smartphones. Some 65.8 million people in the U.S. owned smartphones through January, up from 63.2 million through December.
Even so, until Nokia launches Windows Phone 7 handsets in 2012 and RIM unveils some new handsets capable of rivaling the current Android and iPhone gadgets, it's not clear what these companies can do to burnish their platforms.