Larry Christenson, winless since May 15, hit a two-run double as the Phillies scored three times in the second inning last night and defeated the St. Louis Cardinals, 6-3, in Philadelphia.

Christenson, with one loss and seven no-decisions in his last eight starts, allowed 13 hits over 8 1/3 innings but was helped by three double plays. He evened his record at 4-4. Tug McGraw finished and got his second save.

"I had trouble with everything tonight," Christenson said. "I felt good warming up, but everything fell apart once I got out there." Added Cardinals Manager Whitey Herzog: "We hit the ball good all night, but they managed to catch them."

Christenson's two-run double off loser Bob Forsch (8-4) broke a 1-1 tie and came after the Phillies had loaded the bases on George Vukovich's single and infield hits by Manny Trillo and Ivan DeJesus. Bob Dernier, who was four for five in the game, singled home DeJesus.

Dernier, who ended a zero-for-21 slump Monday night, also scored twice. He doubled to lead off the first and came in on Gary Matthews' sacrifice fly. In the fourth, he started a two-run inning with a two-out single, scoring on a triple by Pete Rose, who was doubled home by Matthews.