CSI TV show star William Petersen will leave cast

The executive producers of the show said Grissom's decision to leave is his own. No further comments were given by show or Grissom's representative. The actor will participate on the show as a guest occasionally and will continue as an executive producer of the program.

"Shows lucky enough to go this long inevitably have to deal with this kind of change," CSI executive producer Naren Shankar told The Associated Press. "Whoever comes in and joins the team after Grissom is going to be a different guy. But the nature of the show and what fans get out of it, that's not going to change," he added.

Petersen's last appearance on air will probably be at the beginning of 2009 on the 10th episode of the season, the Associated Press reported quoting executive producers.

William Petersen, originally from Illinois, was nominated for a Golden Globe Award for his portrayal of Gil Grissom in 2003. CSI is one of CBS Corp.'s TV hits. Last season the CSI series was the top-rated at the network, ranking No.9 among all shows, attracting an estimated of 17 million viewers per week.

Petersen is also a film and theater actor.