Five has been running interactive advertising campaigns since September, but the launch of ETV marks the first time that viewers will be able to visit an interactive application during a programme transmission.
The service means that when viewers press the red button to go interactive during one of five's programmes, they will be directed to a betting facility provided by Sky Bet, as well as a range of generic programme information.
Five is looking for other commercial partners to use its ETV capability, such as gaming and travel providers.
Both ITV and Channel 4 already run ETV with commercial partners.
Five's service launches today (Thursday) during the two Uefa Cup-tie matches that will be shown exclusively on the channel. Sky Bet is supporting the service by sponsoring all of five's live football output through to the end of the 2005-2006 season.
As well as the Sky Bet facility, football-related content provided by Sunset + Vine will be available in the interactive location. Five is planning to create additional appropriate content for other key programming strands.
Jon Lewis, the head of commercial development at five, said: "Five's commercial development team was set up to facilitate just this type of arrangement. Our broad remit allowed us to construct a proposition combining sponsorship and interactivity, totally integrated with programming and the launch of our new ETV service."