Microsoft says retailers sold over 1.5 million Windows Phone 7 handsets during the platform's first six weeks on the market.
"Sales are ramping well as our reputation is growing for offering users a unique experience and are in line with our expectations - especially when compared to other new platform introductions," said Achim Berg, vice president of business and marketing for Windows Phones.
"We are pleased that phone manufacturers sold over 1.5 million phones in the first six weeks, which helps build customer momentum and retail presence."
Berg also said that 18,000 developers are making products for the Windows Phone 7 marketplace, and that over 4,000 apps are currently available.
"We know we have tough competition, and this is a completely new product. We're in the race - it's not a sprint but we are certainly gaining momentum and we're in it for the long run," he added.