Fast National ratings for Thursday, December 17, 2009.

CBS controlled Thursday night with new episodes of "Survivor: Samoa," "CSI: Crime Scene Investigation" and "The Mentalist." Even with NBC doing solid demo numbers for "Saturday Night Live: A Very Gilly Christmas," "Survivor" was the night's top show among adults 18-49, while "The Mentalist" was the evening's most watched program.
Among adults 18-49, CBS won the night with a 3.6 rating, topping the 2.6 rating for NBC in the all-important demographic. FOX's 1.5 rating and the 1.0 rating for ABC were close behind. The CW's 0.8 rating wasn't far back in fifth.
Overall, CBS had an even bigger victory, averaging 14.57 million viewers to go with an 8.9 rating/15 share. NBC's 4.3/7 was a distant second, with FOX's 3.5/6 and the 2.7/4 following. The CW trailed with a 1.2/2.
Although it won the hour with a 7.3/12 and a 3.9 demo rating, CBS' "Survivor: Samoa" was solidly down from last week. Perhaps the long-running reality show has audience overlap with the "Saturday Night Live: A Very Gilly Christmas," which did a 4.9/8 overall and a 3.0 rating in the demo. FOX's "Bones" repeat was third with a 4.3/7, beating NBC's "Grey's Anatomy" repeat. The latest installment of The CW's "Vampire Diaries" marathon had a 1.2/2 for the hour.
CBS stayed in front at 9 p.m. with a 9.5/15 for "CSI: Crime Scene Investigation," which did only a 3.5 rating in the key demo. NBC's "SNL" special was second with a 4.6/7 and a 3.2 rating in the demo. ABC's "Grey's Anatomy" repeat had a 3.0/5, beating the 2.6/4 for FOX's "Fringe" repeat. The CW's "Vampire Dairies" trailed.
"The Mentalist" averaged 15.72 million viewers in the 10 p.m. hour to go with a 9.9/17 and a 3.5 demo rating. NBC's "The Jay Leno Show" was second with a 3.4/6. That left ABC's "Private Practice" in third.
All ratings information comes from preliminary Fast National Nielsen data, which includes live and same-day DVR viewing. All numbers are subject to change.