HOUSTON - Cincinnati manager Bob Boone marveled at how Ryan Dempster has turned himself into a quality major league pitcher.

''He's got good stuff and he's really gotten smooth,'' Boone said. ''When we got him, he was a thrower. But he has smoothed out his delivery.''

Dempster scattered seven hits over nine innings and Jason LaRue hit his first home run of the season in the 10th inning to beat the Houston Astros 2-1 on Tuesday night.

''The thing about Dempster is he is a horse,'' Boone said. ''But now he's gotten pitch efficient. He's a pitcher now. When he came to us, he was a thrower with a real good arm. Now he's come up with a changeup and he's throwing the ball over the plate.''

Dempster said he has a better understanding of what it takes to be a pitcher.

''Before, I would just think about blowing guys away and throwing harder and harder and harder,'' he said. ''Now I'm learning to take a little off of the pitches.''

Dempster (1-0) allowed two walks and struck out three as he topped a strong showing by Houston's Roy Oswalt.

''You've got to bear down against a guy like Oswalt and a lineup like they have,'' Dempster said. ''They're one of the best in the National League and you've got to go out there with your game plan and stick to it. I haven't been striking out a lot of guys. But I also haven't been throwing a lot of pitches. I'll take that any time.''

Scott Williamson pitched a perfect 10th for his second save.

Octavio Dotel (0-1) relieved to start the ninth and gave up the homer to LaRue, who went 3-for-4 and also drove in Cincinnati's first run. It was the first homer Dotel allowed since last June 20, a stretch of 56 innings over 49 outings.

''He did an excellent job with that at-bat,'' Boone said of LaRue. ''I think we will see a lot more of that this season, but time will tell.''

Oswalt, 6-0 against Cincinnati, allowed four hits in eight innings and struck out six.

''My curveball is coming around,'' he said. ''I'm finally getting the feel of it. I felt stronger as the game went on, but I knew I was probably finished after the eighth because I had 119 pitches.''

Houston, which outhit the Reds 7-5, had runners on in every inning except the seventh and 10th, but hit into five double plays.

''Action at the end of a pitch gives you chances for double plays and groundballs, and Dempster has that,'' Boone said.

Cincinnati put runners at first and second in the ninth before pinch-hitter Jose Guillen bounced into an inning-ending double play.

Houston took a 1-0 lead in the first when Craig Biggio walked and scored as Lance Berkman hit into a double play.

Cincinnati tied it in the second on Reggie Taylor's triple and LaRue's infield single.

Notes: Houston C Brad Ausmus has thrown out five of seven runners attempting to steal. … Cincinnati relievers have allowed one of 14 inherited runners to score in seven games. … Reds starters have walked 20 while striking out 14 in 40 innings.