RIM and Apple remain No. 1 and 2 respectively, though both lost a little share between the May-June-July period and the February through April period as measured by ComScore. RIM has a 39.3% share (down 1.8%) of US smartphone subscribers based on operating system and Apple boasts 23.8% (down 1.3%).
Android's share jumped from 12% to 17%, buoyed by a slew of new devices. HTC gave Android another boost this week with the introduction of two new Desire smartphone models.
The ComScore findings come on the heels of Gartner projecting that Android by year-end will be No. 2 worldwide only to Nokia's Symbian and separately, new Nielsen numbers show Android devices last quarter outsold iPhone devices for the first time.
New numbers from Google show that customers are increasingly buying devices with its newest version of Android, dubbed Froyo, a sign that fragmentation of the Android market might lessen.
Not all numbers are going Android's way. Last week one measurement company showed Apple iOS beats Android 6-to-1 worldwide in market share.)
The expected arrival of Windows Phone 7, on 11 October can't come soon enough for Microsoft, which saw its share fall from 14% to 11.8%.
Despite share drops by Microsoft and the others, ComScore does note that the overall market keeps growing, with 53.4 million people in the US owning smartphones during the measurement period.
Mobile content usage is also on the rise, with ComScore showing increases in text messaging, downloaded apps and social networks accessed by smartphone users.
Samsung, LG, Motorola, RIM and Nokia were the leading mobile OEMs during the three-month period measured by ComScore, in that order, as was the case in the three months before.
See also: Group test: what's the best smartphone?