CBS captured the second Thursday of the May sweep in all key ratings categories behind timeslot victories for “Survivor: Palau” and “CSI,” according to preliminary nationals from Nielsen.

From 9 to 10, “CSI” delivered the night’s top averages (8.8 rating/23 share in adults 18-49, 25.9 million viewers overall), easily besting NBC’s “The Apprentice 3” (5.7/15 in 18-49, 12.8 million viewers overall). The Eye won by an even bigger advantage in the night’s opening hour, with “Survivor: Palau” (6.8/21 in 18-49, 19.7 million viewers overall) more than doubling NBC comedies “Joey” (3.0/10 in 18-49, 7.5 million viewers overall) and “Will & Grace” (3.3/10 in 18-49, 7.5 million viewers overall).

NBC salvaged the final hour of the evening, as “ER” (7.0/19 in 18-49, 15.5 million viewers overall) toppled CBS’ “Without a Trace” (5.3/14 in 18-49, 18.3 million viewers overall) in all under-55 categories, opening up an especially big advantage in the 10:30 half-hour. “Trace” remained on top in total viewers.

Fox had one of its best Thursdays of the season with back-to-back episodes of “The OC” at 8 (3.0/9 in 18-49, 6.6 million viewers overall) and at 9 (3.4/9 in 18-49, 7.2 million viewers overall). Soph sudser beat NBC’s opening-hour comedies among viewers under 50.

ABC was a distant fourth but above its Thursday season average with the network premiere of theatrical “Sweet Home Alabama” (2.0/6 in 18-49, 7.3 million viewers overall) and “Primetime Live” (2.2/6 in 18-49, 7.3 million viewers overall).

Preliminary 18-49 averages for the night: CBS, 7.0/19; NBC, 5.3/15; Fox, 3.2/9; ABC, 2.1/6; UPN, 1.7/5; WB, 1.3/4.

In total viewers: CBS, 21.3 million; NBC, 11.9m; ABC, 7.3m; Fox, 6.9m; UPN, 4.5m; WB, 2.9m.