Riding the wave of new handset introductions and wide carrier distribution in the second quarter (Q2), the Android smartphone operating system (OS) continued its upward climb in the U.S. consumer mobile phone market, according to The NPD Group, a leading market research company.

For the first time since the fourth quarter (Q4) of 2007, RIM fell to second position, as Android took the lead among operating systems in handsets sold to U.S. consumers. NPD's latest wireless market research reveals that Android accounted for 33 percent of all smartphones purchased in Q2, ahead of RIM (28 percent) and Apple (22 percent).

Based on U.S. consumer purchases of mobile phones in Q2, the top 5 Android smartphones were as follows:

1.Motorola Droid

2.HTC Droid Incredible

3.HTC EVO 4G

4.HTC Hero

5.HTC Droid Eris

Model selection and promotions continue to play a role in the race for carrier dominance. According to NPD's Mobile Phone Track, Verizon Wireless has maintained its lead among top carriers for the last three quarters comprising a third (33 percent) of the units sold in the U.S. mobile phone market in Q2, followed by AT&T (25 percent), Sprint (12 percent), and T-Mobile (11 percent). In Q2 Verizon Wireless continued their buy-one-get-one (BOGO) offers on all smartphones, including both RIM and Android models.

In spite of an overall decline in the number of mobile phones purchased year over year, the ongoing popularity of both messaging phones and smartphones, which are generally more costly than standard feature phones, resulted in slightly higher prices for all mobile phones in Q2. The average selling price for all mobile phones reached $90, which is a 3 percent increase since Q2 last year. Smartphone unit prices, by comparison