Fast National ratings for Thursday, Sept. 3, 2009.

Viewers tuned in to CBS to watch "Big Brother" split up Jeff-and-Jordan and stuck around for the rest of the evening, as the network dominated Thursday in all key measures.

Among adults 18-49, CBS averaged a 2.5 rating, well ahead of the 1.7 rating for FOX and NBC's 1.6 rating. ABC was fourth in the key demographic with a 1.3 rating, followed by the 0.6 rating for The CW.

Overall, CBS averaged an estimated 9.375 million viewers to go with a 6.0 rating/10 share. None of the other networks were close, with FOX's 3.4/6, NBC's 3.3/6 and ABC's 3.1/5 following in a clump. The CW was fifth with a 1.1/2.

In the 8 p.m. hour, CBS got a strong 5.4/10 from "Big Brother," which also delivered a 2.7 rating in the 18-49 demographic, the night's highest. FOX's "Bones" had a 3.8/7 for second, while ABC's "Grey's Anatomy" and NBC's "30 Rock" and "Parks and Recreation" tied for third (advantage NBC in both viewers and 18-49). The CW's "Supernatural" was fifth with a 1.2/2.

"CSI: Crime Scene Investigation" was up to a 6.1/10 for CBS in the 9 p.m. hour (but lost 18-49 viewership from its lead-in). ABC's "Grey's Anatomy" was second, beating the 3.1/5 for NBC's "The Office" and "30 Rock." FOX's Twitter-enhanced "Fringe" had a 3.0/5, dropping in both viewers and 18-49 rating from its "Bones" lead-in. The CW's "Supernatural" had a 1.1/2.

"The Mentalist" closed the night with a 6.5/11 for CBS. NBC's "Law & Order" had a 3.5/6 for a distant second. ABC's "Private Practice" trailed.

 

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