Fast National ratings for Thursday, March 12, 2009.

NBC's "E.R." got a big George Clooney-related boost at 10 p.m., but even his star power couldn't prevent CBS from sweeping the primetime hours.

CBS won the key 18-49 demographic with a 3.7 rating, beating the 3.5 rating for ABC and NBC and FOX's 3.1 rating. The CW was well back in fifth with a 1.3 rating.

Overall, CBS averaged an estimated 13.88 million viewers and an 8.3 rating/13 share, better than the 6.7/11 for ABC. FOX was third with a 5.2/8, leaving NBC in third with a 4.6/7. The CW's 2.0/3 was good enough for fifth. 

At 8 p.m. CBS got a 7.4/12 for "Survivor: Tocantins." FOX was second with a 5.9/10 for "Bones," while the 4.9/8 for ABC's "Ugly Betty" was third. NBC's  "My Name Is Earl" and "Kath & Kim" barely beat the 2.2/4 for The CW's "Smallville."

CBS stayed on top at 9 p.m. as "CSI: Crime Scene Investigation" did a 10.3/16, down from last week's Taylor Swift episode. ABC's "Grey's Anatomy" was second with a 9.0/14. FOX's "Hell's Kitchen" was a distant third, nipping the 4.2/6 averaged by "The Office" and "30 Rock." The CW's "Smallville" was fifth with a 1.7/3.

"Eleventh Hour" finished CBS' sweep with a 7.4/12. Rumors of guest cameos pushed "E.R." to a 6.9/12 for NBC. The medical drama also won the hour in the 18-49 demo. ABC's "Private Practice" finished second in the demo, but third overall.

All ratings information comes from preliminary Fast National Nielsen data, which includes live and same-day DVR viewing. All numbers are subject to change.