ABC’s Thursday night gamble paid off big-time. The network, for years a non-factor on the night, knocked off CBS for No. 1 last night in both adults 18-49 and households with a huge premiere for “Grey’s Anatomy.”

“Anatomy,” which moved from Sunday to Thursday, averaged a 10.9 adults 18-49 rating at 9 p.m., according to Nielsen, trouncing CBS’s long-dominant “CSI” by 3.4 points.

That led ABC to victory on the night with a 7.2 rating and 19 share, comfortably ahead of second-place CBS’s 6.0/16, down 21 percent from last year's premiere night, and third-place NBC’s 4.8/12, even with last year. It was ABC's first opening Thursday win since at least 1991.

Among households, ABC narrowly edged CBS with an 11.2/18 to the latter’s 11.0/17.

On a night with many big storylines, “Grey’s” huge audience was the biggest. Not only did the show beat “CSI” in 18-49s, where many media people had expected it to win, but it also topped the crime drama among total viewers, averaging 25.14 million to the latter’s 22.04 million.

Among 18-49s, “CSI” was down 9 percent from last season’s 8.2 average. Meanwhile “Grey’s” bettered last season’s 8.7 average by 25 percent.

Each of the Big Three networks led one hour during the night. NBC, whose “ER” had faded against CBS’s “Without a Trace” over the past few years, surged back into a dominant first place at 10 p.m., averaging a 6.8, a full point ahead of ABC’s new drama “Six Degrees” and 2.6 ahead of the somewhat disappointing premiere of CBS’s new “Shark.” “ER” was up 6 percent over last season’s debut.

“Shark” lost 44 percent of “CSI’s” lead-in, averaging a 4.2 and falling from a 4.5 to a 4.0 in its second half hour. It did beat “Degrees” in total viewers, averaging 14.95 million to the latter’s 13.34 million.

“Degrees” lost 47 percent of its considerable lead-in, averaging a 5.8 in adults 18-49. The show dipped steeply at 10:30 p.m., falling from a 6.6 to a 4.9.

Next week ABC premieres “Ugly Betty,” the highly praised new dramedy, at 8 p.m. That could have a big effect on the night, as could the second-week performances of “Degrees” and “Shark.”

Meanwhile, big ratings for other networks left Fox and the CW few leftovers. Univision was fourth at 2.0/5. Fox averaged a 1.6/4 on the night, followed by the CW at 1.0/3 with reruns.

At 8 p.m., CBS’s “Survivor” placed first easily with a 6.4, followed by a 4.8 for ABC’s “Grey’s Anatomy” clips show. Perhaps most notable in the hour, NBC’s Emmy winner “The Office” bested lead-in “My Name is Earl” for the first time in 18-49s, averaging a 4.3 to the latter’s 3.7. It was “Office’s” best showing since last March.

Univision’s “La Fea Mas Bella” was fourth at 2.1. Fox was fifth with series lows for “’Til Death” (2.2) and “Happy Hour” (1.7). The CW’s “Smallville” was sixth at 1.1.

At 9 p.m., after “Grey’s” 10.9 and “CSI’s” 7.5, NBC’s “Deal or No Deal” was third at 3.5, followed by Univision’s “Barrera de Amor” at 2.1, Fox’s “Celebrity Duets” at 1.2, and CW’s “Supernatural” rerun at 0.9.

At 10 p.m., “ER’s” 6.8 led, followed by “Degrees” at 5.8, “Shark” at 4.2, and Univision at 1.8.

In households, ABC was first and CBS second, followed by NBC at 7.4/12, Fox at 2.9/4, Univision at 2.3/4 and the CW at 1.6/2.