Android, Apple capture still more U.S. smartphone users.

Android remains firmly on top, but Apple's iOS also saw a boost in market share over the three months ended July, says ComScore.

Android and Apple continue to bite bigger hunks out of the U.S. smartphone market.

As of the three months ended July, Google's mobile OS held a 52.2 percent share of the market, a gain of 1.4 points from the prior three months, ComScore said today. In second place, Apple's iOS grabbed 33.4 percent of the market, up 2 points from the prior period.

That left the rest of the top five platforms still spinning down the drain.

RIM's BlackBerry OS took third place with a 9.5 percent share, down 2.1 points from the previous three months. Microsoft's Windows Phone took home 3.6 percent of the market, a loss of almost half a percentage point. And Nokia's Symbian trailed with just 0.8 percent of the market, down half a percentage point.

For the first time, Samsung's Galaxy S3 surpassed the iPhone as the top-selling smartphone in the U.S., according to Canaccord Genuity analyst T. Michael Walkley. The analyst's retail checks found increased demand for the S3 but lighter sales for the iPhone 4S last month. A dip for Apple's flagship phone isn't a surprise, though, as iPhone buyers typically delay purchases in advance of a new model.

Apple today sent out invitations for a September 12 event in which it's expected to unveil the next-generation iPhone.

Among mobile phone manufacturers, Apple enjoyed the biggest gain in market share, winning almost 2 points to give it 16.3 percent of the market, ComScore noted. But the iPhone maker remained in third place behind Samsung and LG, which grabbed 25.6 percent and 18.4 percent of the market, respectively.