His AudioNet service (www.audionet.com) rebroadcasts live TV and radio signals, now totaling 175 radio stations and 3 TV stations. That number is expected to grow to 300 radio stations and 16 TV stations by yearend.
He recently added the widely carried Rush Limbaugh talk show, along with live Webcasts of major sports events. Radio stations pay AudioNet by donating ad space to promote it, or by allowing AudioNet to resell the space.
"We're far more compelling than a traditional Web site," said Mr. Cuban, who launched Dallas-based AudioNet in 1995.
In the still-small Internet radio community, Mr. Cuban has a presence that puts a public face on the blossoming business.
Current estimates of the number of radio stations broadcasting live online may total 430, said Peggy Miles, president of Intervox Communications consulting, up from 56 a year ago.
AudioNet has already attracted advertisers including Visa USA, IBM Corp. and AT&T Corp., which run ads that have audio and visual elements.
Mr. Cuban's site allows users to listen to a station while using their computer for other activities; the audio follows users from site to site.
But Mr. Cuban believes the real advantage of an online radio station is in reaching a hard-to-reach demographic.
"You can't reach white-collar workers at their desks," he said.
While acknowledging that 70% of radio listeners are local, he pointed out that people will tune in for sports broadcasts they can't get locally. AudioNet can "fill in holes, like in New York, where there is no country station."