YouTube has begun hosting full-length TV episodes, accompanied by intrusive ads for the Google-owned online video site.
The selection of reruns from CBS was less than impressive - five episodes each of Beverly Hills 90210, MacGyver, Star Trek: The Original Series, plus 14 episodes of The Young and The Restless.
But the move is seen as a first attempt by YouTube to become a major platform for showing advertising-supported TV shows over the internet.
Other websites already show advertising-supported shows. Many are online versions of existing cable and TV channels, while some like Veoh.com, Joost.com and Hulu.com are internet-only sites.
Friday's move is the second major initiative by Google this week to make money from YouTube.
The web giant bought the site for $US1.65 billion ($A2.4 billion) in 2006, but despite experimenting with different advertising formats it never managed to translate YouTube's huge audience into advertising riches.
Earlier in the week Google added shopping features to the service, by enabling users to click on links beneath videos to make related purchases.
The new advertising includes 15-second segments before, during and after each show. Google had previously dismissed such ads as unsuitable for a web-viewing environment where the attention span of the audience is thought to be short.
