AT&T ( has reported first-quarter results highlighted by strong 4G mobile data sales and wireless margins, and solid revenue and earnings growth. And it continues to move lots of iPhones.

AT&T sold 5.5 million smartphones, exceeding a first-quarter sales record set last year. Smartphones represented more than 78 percent of postpaid device sales. At the end of the quarter, 59.3 percent, or 41.2 million, of AT&T’s postpaid subscribers had smartphones, up from 46.2 percent and 31.5 million a year earlier.

Both iPhone and Android device sales remain strong. iPhone sales were helped by AT&T’s 4G network, the company says. In the quarter, the company activated 4.3 million iPhones, with 21% new to AT&T.

“We continue to capitalize on our terrific momentum in mobile Internet,” says Randall Stephenson, AT&T chairman and CEO. “Smartphone and branded computing device sales continue to set a record pace, mobile data revenues were up nearly 20 percent, and we achieved this growth with expanding margins. These results add confidence in our outlook for the year.”