Fast National ratings for Friday, April 23, 2010.
 
NBC scored an unusually commanding Friday win, taking all three hours both overall and in the key demo, aided by repeats for CBS' early dramas and the continued slide for "Miami Medial."
 
Among adults 18-49, NBC averaged a 1.5 rating, topping the 1.2 rating for ABC and CBS' 1.0 rating. FOX's 0.9 rating and the 0.8 rating for The CW followed in the all-important demographic.
 
Overall, NBC averaged an estimated 6.84 million viewers and a 4.6 rating/8 share. CBS moved up to second with a 3.3/6, with ABC's 2.6/5 taking third. FOX's 1.9/4 was fourth, with The CW's 1.2/2 trailing.
 
NBC's "Who Do You Think You Are?" (featuring Susan Sarandon) was first in the 8 p.m. hour with a  4.2/8 and a 1.3 demo rating. CBS' repeat of "Ghost Whisperer" was second with a 3.0/6, beating the 2.2/4 for ABC's "Wife Swap." A repeat of "House" on FOX finished fourth overall, beating the 1.4/3 for "Smallville," which was up for last week, averaging 2.235 million viewers and finishing fourth in the demo with a 1.0 rating.
 
"Dateline NBC" did a 4.5/8 and a 1.4 demo rating in the 9 p.m. hour for NBC. CBS' "Medium" repeat was second. The season finale of ABC's "Jamie Oliver's Food Revolution" had a 2.5/4 and finished second in the demo. FOX's encore of Tuesday's "Glee" had a 1.8/3 for fourth. The CW stayed fifth with an "America's Next Top Model" repeat.
 
In the 10 p.m. hour, NBC's "Dateline" improved to a 5.0/9 and a 1.7 rating in the demo. CBS' "Miami Medical" was second with a 4.0/7, with its audience falling to just over 6 million and its demo rating falling to a 1.0 rating. The CBS freshman drama has declined in viewers and the demo every week since its premiere. Third place overall went to ABC's "20/20," with a 3.0/5, though it still topped "Miami Medical" in the demo.
 
 
All ratings information comes from preliminary Fast National Nielsen data, which includes live and same-day DVR viewing. All numbers are subject to change.