Android tied with iOS in October as the smartphone operating systems most often hitting Millennial Media's mobile advertising network.
In a report released Thursday, Millennial said that Android and iOS accounted for 37 percent of traffic on its network in the US in October. IOS includes the iPhone, iPod Touch and iPad.
In the previous month, iOS made up 46 percent of traffic and Android had 29 percent.
For the first time, Symbian made a showing in Millennial's report of US smartphones, accounting for a two percent share of hits on Millennial's network. Nokia has long struggled for a foothold in the US market but in late September began shipping the N8, a phone running the latest Symbian operating system.
Among manufacturers, Apple held on to the number one spot with Samsung becoming number two and Motorola slipping to third place. Research In Motion took fourth place by manufacturer but among individual handsets had the number two phone with the BlackBerry Curve. In the previous month, the Motorola Droid came in second in terms of handset models, behind the iPhone.
Thirteen Android and six RIM devices were in the top 30 mobile devices.
Counting US and non-US traffic, Android has shown the most growth since January, Millennial found. Requests from Android phones have grown 2182 percent, Millennial said. Apple requests increased 32 percent over that time period and RIM increased 243 percent.
Millennial says it collects the most data from mobile users of any independent mobile ad provider. AdMob used to release similar monthly reports of mobile traffic but quit shortly after Google acquired the company.