Infinity launched the Jack format in New York City and Chicago today. WCBS-FM in New York City made the switch at 5 p.m. ET, kicking off the new programming with "Fight For Your Right (To Party)" by the Beastie Boys. In Chicago, WJMK-FM launched Jack at 4 p.m. CT.

The WCBS-FM Oldies format will continue to exist as an online radio station (www.wcbsfm.com). WJMK-FM will also transfer its Oldies format online at www.WJMK.com.

"These are the songs that we all loved growing up, but haven't heard in years," said WJMK-FM VP/GM Dave Robbins. "But this station is about more than just the music - it's about being a true reflection of our great city's culture. We couldn't be more excited to debut Chicago's newest and most unique radio station."

Infinity Broadcasting launched its first Jack station in July 2004 at KJKK-FM in Dallas. The station has improved its position from 28th to 5th, and currently ranks as the most listened to station in the market with adults 25-54. Jack format changes have also occurred at stations in Los Angeles, Baltimore, Minneapolis, Seattle, and Buffalo.