On Tuesday , Sprint also announced a glasses-free 3D smartphone, the HTC Evo 3D, which runs on its 4G WiMax network.
Neither company has announced pricing for their 3D phones, but analysts said they need to be in line with the $200 to $250 price of other smarphones to be accepted.
Still, some believe early adopters will pay a premium price for them, mainly to use them for gaming and viewing of other video content.
"They'll probably sell a lot so people can watch porn on them," said Jack Gold, an analyst at J. Gold Associates. "I'm being serious about porn, and people will like the 3D porn, sad as that is."
For most customers, 3D will take a lot of getting used to, since there really aren't that many applications now available with 3D, Gold said. "It will take a long time to catch on, because people don't know what 3D is good for."
The LG Thrill will come with a 4.3-in. display and a dual core 1GHz processor, the HTC Evo 4G comes with a 1.2 GHz dual core chip.
The Thrill comes with a 5-megapixel stereoscopic camere and runs 2.2. It has 16GB of storage and plays video back through an HDMI port.
The other smartphone that AT&T announced was the HTC HD7S, which runs Windows Phone 7 on a 4.3-in. display, and has a 1GHz processor and a 5-megapixel camera.
AT&T plans to deliver 20 4G phones in 2011, running on HSPA+, which has theoretical download speeds of 21 Mbit/sec.
AT&T plans to launch LTE in mid-year in the U.S.
Matt Hamblen covers mobile and wireless, smartphones and other handhelds, and wireless networking for Computerworld. Follow Matt on Twitter at or subscribe to . His e-mail address is .
in Computerworld's Smartphones Topic Center.