The Las Vegas-set drama "21" held at No. 1 in U.S. theaters for a second week, estimated weekend ticket revenues showed Sunday.

The movie, based on a real-life story about college students going to the gambling capital in an attempt to take the casinos for millions, tallied $15.1 million in its second week, Box Office Mojo reported.

George Clooney's old-time football comedy "Leathernecks" opened at No. 2 with $13.49 million in ticket sales and Jodie Foster's adventure comedy "Nim's Island" started out at No. 3 with $15.3 million in receipts.

"Dr. Seuss' Horton Hears a Who!" slipped from second to fourth at $9.1 million, while another new offering, "The Ruins," a Scott B. Smith written and directed horror movie, opened at No. 5 with $7.84 million.

Filling out the top tier were "Superhero Movie," $5.41 million; "Tyler Perry's Meet the Browns," $3.51 million; "Drillbit Taylor," $3.5 million; "Shutter," $2.88 million; and "10,000 B.C.," $2.77 million.

Dropping out of the Top 10 were: "Stop-Loss,""College Road Trip" and "The Bank Job."