Denny Gonzalez hit a two-run homer and Rick Reuschel pitched his sixth straight complete game, striking out 12 batters, as Pittsburgh, playing at home, defeated Chicago.
Gonzalez's homer was his fourth of the season and came in the second inning against Steve Engel (1-4). It followed a two-out double by Tony Pena.
Reuschel (12-7) gave up eight hits and had a season high in strikeouts as he beat his former teamates for the second time this season.
"His arm didn't look as strong as it does now," said Cubs Manager Jim Frey. "He's a lot stronger and a lot sharper with his pitches. A comeback like his happens, but it doesn't happen very often."
"He gives us stability, leadership, and the ability to show out young pitchers how it's done," Pirates Manager Chuck Tanner said of Reuschel, 36.
"I'm in a groove right now," said Reuschel. "It's probably the longest I've ever been in one. I hope it continues."
His strikeout total was one short of the career high he established in 1973. He was unimpressed with the feat.
"I don't like strikeouts," Reuschel said. "It takes too many pitches. I'd rather make them hit the first or second pitch and make an out."