Marcus Thornton scored 30 points and LSU held off a late rally to beat Butler 75-71 on Thursday in the first round of the NCAA tournament.
Tasmin Mitchell had 14 points and Chris Johnson added 12 points for the Tigers (27-7), seeded eighth in the South Regional. They advanced to Saturday's second round against the North Carolina-Radford winner.
Matt Howard scored 22 points before fouling out with 35.7 seconds left for No. 9 seed Butler.
The Bulldogs (26-6) made things interesting by twice pulling within three in the final minute. The last came when Willie Veasley tipped in Gordon Hayward's missed 3 with 5.4 seconds left made it 74-71, before Johnson hit one of two free throws with 4.5 seconds left to seal it.
Hayward, Butler's top 3-point shooter, finished with 12 points for the Bulldogs, who lost in the first round for the first time since 2000.