Fast National ratings for Wednesday, Aug. 18, 2010.
 
Summer reality shows were Wednesday night's big draws, with "Big Brother," "America's Got Talent" and "Masterchef" boosting CBS, FOX and NBC all to shares of the nightly ratings crowns.
 
Among adults 18-49, it was FOX coming out on top with a 2.1 rating, edging the 1.8 rating for CBS and NBC in the key demographic. ABC's 1.4 rating was fourth, with The CW's 0.5 rating trailing.
 
Overall, though, CBS and NBC both had a 4.2 rating/7 share, though NBC's average of 6.855 million viewers topped the estimated 6.481 million viewers for CBS. FOX was far back in third with a 3.0/5, beating the 2.5/4 for ABC and The CW's 0.9/2.
 
CBS started the night in first with "Big Brother," which continued its rise with a 4.4/8 and a 2.6 demo rating, up from last Wednesday's show in all measures. NBC's "Minute to Win It" was second with a 3.5/6, beating the 2.8/5 for FOX's "Masterchef," which finished second in the demo. ABC's repeats of "The Middle" had a 2.7/5, leaving The CW in fifth with an "America's Next Top Model" repeat.
 
NBC moved into first with a 6.0/10 for an "America's Got Talent" results show, which drew the night's biggest audience and won the 9 p.m. hour with a 2.5 demo rating. CBS' repeat of "Criminal Minds" was second with a 4.4/7. FOX's "Masterchef" improved to a 3.1/5 and finished second in the demo. ABC's repeats of "Modern Family" and "Cougar Town" were fourth, with The CW's new "Plain Jane" doing a 0.8/1 (up from last week in total viewers) for fifth.
 
CBS' "CSI: NY" had a 3.7/7 to win the 10 p.m. hour overall. NBC's "Law & Order: Special Victims Unit" was second overall and won the hour with a 1.4 demo rating. ABC's "Castle" had a 2.7/5 for 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.