The iTunes store will offer 11 shows from NBC, USA Network and the Sci Fi Channel that range from oldies such as the 1950s cop show "Dragnet" to current shows such as "The Tonight Show with Jay Leno."
Apple is charging $1.99 per episode for the television downloads, as well as for music videos and short films. The newly produced shows will be available for download a day after they air on TV.
The addition of NBC's television shows to the iTunes inventory comes assuch as broadcast affiliates and cable services. Telephone companies such as and online giants Google, Yahoo and America Online are also poised to jump into the market.
In October, the Walt Disney Company's television network, ABC, and Disney's cable network began offering five television shows for download via iTunes.
Apple said Tuesday that it has now sold more than 3 million videos from its iTunes store since, indicating that customer demand extended beyond simple one-time curiosity.
"It has continued growing, and at a faster pace than when we started," said Eddie Cue, Apple's vice president of iTunes. "It's not like people are downloading once and not coming back."
Other shows now offered for download include the 1980s hit "Knight Rider," "Alfred Hitchcock Presents," and the recent remake of "Battlestar Galactica." Most of the older shows will initially offer only the first season, but later seasons will be added over time, Cue said.
The iTunes TV catalog now offers 16 shows.