Fast National ratings for Thursday, August 23, 2012.
 
A repeat of "Big Bang Theory" drew Thursday night's biggest overall audience, while a double-elimination episode of "Big Brother" drew the biggest audience among young viewers, helping CBS win primetime in both measures.
 
Note that some very minor shifting may occur due to NFL preseason preemptions in some markets.
 
Among adults 18-49, CBS averaged a 1.8 rating for Thursday night, beating ABC's 1.5 rating in the key demographic. NBC averaged a 1.0 key demo rating, bettering the 0.7 key demo rating for FOX and The CW's 0.3 key demo rating.
 
Overall, CBS averaged an estimated 6.205 million viewers and a 4.0 rating/7 share for the night. ABC was second with a 3.1/5 and 5.17 million viewers, with NBC's 2.7/5 and 4.07 million viewers in third. FOX averaged a 1.4/2 and 2.11 million viewers, while The CW averaged a 0.6/1 and 874,000 viewers.
 
[Univision averaged 3.37 million viewers and a 1.3 rating among adults 18-49 for Thursday night.]
 
8 p.m. - Repeats of "The Big Bang Theory" and "Two and a Half Men" helped CBS start primetime in first with 6.89 million viewers and a 1.9 rating among adults 18-49. ABC's "Wipeout" was second with 5.43 million viewers and a 1.5 key demo rating. Repeats of "The Office" and "Parks and Recreation" averaged 3.045 million viewers and a 0.9 key demo rating for NBC, compared to the 2.135 million viewers and 0.8 key demo rating for repeats of "Raising Hope" and "New Girl" on FOX. The CW averaged a 0.6/1 and 914,000 viewers for "Oh Sit!," which may be up a hair from last Thursday's airing.
 
9 p.m. - Thursday's "Big Brother" installment averaged 6.36 million viewers and a 2.2 rating among adults 18-49 for CBS in the 9 p.m. hour. ABC's "Wipeout" remained second with 5.39 million viewers and a 1.7 key demo rating. NBC's "Saving Hope" averaged 3.74 million viewers and a 0.8 key demo rating, with FOX's "Glee" repeat following with 2.08 million viewers and a 0.7 key demo rating. "The Next: Fame Is At Your Door" averaged 835,000 viewers and a 0.3 key demo rating, basically flat in its second week.
 
10 p.m. - NBC's "Rock Center with Brian Williams" won the 10 p.m. hour overall with 5.42 million viewers and tied for the lead with a 1.2 rating among adults 18-49. CBS' repeat of "Person of Interest" was second with 5.36 million viewers and third with a 1.1 key demo rating. On ABC, "Rookie Blue" was down in viewers with 4.69 million viewers and steady with a 1.2 key demo rating.
 
All ratings information comes from preliminary Fast National Nielsen data, which includes live and same-day DVR viewing. All numbers are subject to change.