CBS rolled to a ratings victory Thursday to kick off the second week of the May sweep, taking advantage of NBC’s faltering comedies.

CBS’ advantage in the opening hour — “Survivor” vs. “Joey” and “Will & Grace” — was the difference on a night when the Eye’s “CSI” scored a sizable victory over “The Apprentice” and the Peacock’s “ER” handled CBS’ “Without a Trace” in all key demos.

CBS won over NBC in adults 18-49 (7.1/19 to 5.4/15), adults 25-54 (8.8/22 to 6.1/15) and total viewers (21.6 million to 12.1 million), cementing its position as the No. 1 network on Thursday for the season, according to Nielsen.

Biggest difference has been in the 8 o’clock hour, where “Joey” has stumbled in the old “Friends” slot and “Survivor” remains potent for CBS.

Last week, “Survivor: Palau” (7.1 rating/21 share in adults 18-49, 20.07 million viewers overall) overwhelmed Joey” (3.0/10 in 18-49, 7.46m) and “Will & Grace” (3.4/10, 7.62m), with “Joey” at all-time firstrun timeslot lows for the Peacock.

Fox’s “The OC” (3.1/9 in 18-49, 6.77m) was just a tick behind the NBC comedies for second place in 18-49 and was a solid No. 2 to “Survivor” in adults 18-34 (3.8/13). With a second “OC” episode at 9 (3.4/9 in 18-49, 7.19m), Fox led the night in femmes 12-34 (5.3/16).

CBS vet crime drama “CSI” stood as the night’s top-rated program (9.0/23 in 18-49, 26.65m), besting NBC’s “The Apprentice 3” (5.8/15 in 18-49, 13.00m) across the board.

NBC bounced back at 10, with “ER” (7.1/19 in 18-49, 15.66m) scoring a comfortable demo victory over “Without a Trace” (5.2/14, 17.92m). “Trace” remained on top in total viewers but fell to firstrun season lows for a regular episode.

ABC was above average but remained deep in fourth with the network preem of “Sweet Home Alabama” (2.1/6 in 18-49, 7.32m).

On Friday, CBS used repeats of the “CSI” franchise to get in the game from 8 to 10 and then put the night in its column with a winning perf from solid rookie “Numbers” at 10 (prelim 3.1/9 in 18-49, 11.4m). It topped NBC’s “Law & Order: Trial by Jury” (prelim 2.9/9 in 18-49, 9.8m) and ABC’s “20/20” (prelim 2.5/8, 7.4m).

The series finale of NBC’s “Third Watch” at 9 (prelim 2.7/9 in 18-49, 8.9m) finished in a virtual 18-49 tie with CBS’ “CSI” repeat (prelim 2.8/9, 10.5m) — with both ahead of ABC’s hourlong season finale of “Hope & Faith” (prelim 2.2/7 in 18-49, 6.2m).

Saturday went easily to Fox with a NASCAR race (roughly 3.4/12 in 18-49, 9 million viewers), while the net preem of “Harry Potter and the Chamber of Secrets” put ABC in second (prelim 2.4/8 in 18-49, 7.9 million).