Fast National ratings for Friday, March 20, 2009.

NCAA Tournament action heated up on Friday night with a number of upsets and overtime thrillers. Perhaps that's why CBS had no trouble topping its rivals in the ratings race.

Among adults 18-49, CBS averaged a 2.9 rating, better than its Friday season average in the key demo. ABC was second with a 1.7 rating, followed by the 1.4 rating for FOX and NBC's 1.3 rating. The CW's 0.6 rating trailed. 

Overall, though, CBS was down from its normal figures, averaging an estimated 8.36 million viewers and a 5.2 rating/9 share. ABC stayed second with a 3.8/7. NBC was third with a 3.0/4, beating the 2.4/4 for FOX. The CW's 1.0/2 was fifth.

CBS' primetime sweep started at 8 p.m. with a 5.1/9 for the NCAA Tournament. ABC's "Wife Swap" was second with a 3.3/6, beating the third place "Howie Do It" on NBC. FOX was a close fourth with a 2.3/4 for "Terminator: The Sarah Connor Chronicles." The CW's new episodes of "Everybody Hates Chris" and "The Game" averaged a 1.1/2.

At 9 p.m. CBS stayed on top with a 5.4/9. ABC's "Supernanny" was second. With its exhaustively hyped sixth episode. FOX's "Dollhouse" grabbed third with a 2.6/5, though its viewership of 4.13 million was actually down from last week. NBC's "Friday Night Lights" had a 2.5/4 for fourth. The CW's "America's Next Top Model" repeat trailed.

Basketball kept CBS in first at 10 p.m. with a 5.1/9. ABC's "20/20" had a 4.5/8 for the hour, nipping "Dateline NBC."

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