No surprise here: Showtime this morning formally picked up its flagship series Dexter for a sixth season. There had been doubt whether the drama starring Michael C. Hall would be able to match the performance of its highly-rated Season 4 featuring John Lithgow, but Season 5, which wraps next week, has done very well, recently posting the show’s second-highest rated episode ever behind the Season 4 finale. Here is the announcement:

LOS ANGELES, CA — (December 6, 2010) — As season five of SHOWTIME’s top-rated drama series DEXTER, starring Emmy-nominated and Golden Globe award-winning actor Michael C. Hall, heads toward another powerful, suspense-filled finale on Sunday, December 12th at 9 PM ET/PT, the network has renewed the series for a sixth season. The announcement was made today by David Nevins, President of Entertainment, Showtime Networks. Season 6’s episodes will go into production next spring in Los Angeles.“DEXTER is the best suspense drama on television,” said Nevins. “To grow its audience so significantly in its fifth season is an enormous accomplishment by this amazing cast and crew. This is the easiest decision I’ve made since I got to Showtime.”

One of the most acclaimed series on television, DEXTER received seven Primetime Emmy Award nominations this year, including Outstanding Television Drama Series, Outstanding Lead Actor in a Drama Series for Michael C. Hall and Outstanding Guest Actor in a Drama Series for John Lithgow, which Lithgow won. Additionally, director Steve Shill won the Emmy for Outstanding Directing for a Drama Series.

DEXTER had its second highest ratings ever with this season’s tenth episode (Nov. 28), delivering 2.54 million viewers, up 43 percent versus the season five premiere (1.77 million). The telecast was the second-highest delivery in the series’ history, behind the season four finale (2.57 million).