Scott Rolen's sacrifice fly in the bottom of the 10th inning provided the winning run, as Cincinnati rallied from a late three-run deficit to beat Chicago, 4-3, in the final contest of a truncated two-game series.
Zack Cosart singled to begin the frame and moved to third when Rafael Dolis (1-2) threw wild to first on a Chris Heisey sacrifice bunt attempt. Rolen then lofted a ball deep enough to right field to bring in the deciding run.
It made a winner of Logan Ondrusek (2-0), who turned in a scoreless top of the 10th. Starter Homer Bailey worked six full frames, yielding nine hits and three runs.
Willie Harris, Joey Votto and Brandon Phillips scored in the ninth for the Reds, who dropped the opener on Wednesday.
Starlin Castro, Bryan LaHair and Geovany Soto hit solo homers for the Cubs, who have lost three of their last five.
Ryan Dempster made the most of his return from the 15-day disabled list, tossing eight scoreless innings. He scattered three hits and walked one while fanning six, but Carlos Marmol wasted that effort in the ninth.
He walked Harris and Votto before Cubs third baseman Ian Stewart booted a Phillips grounder, allowing a run to score. Jay Bruce followed with a single to load the bases, and Ryan Ludwick then walked to force in a run and make it 3-2. Dolis was called on and induced Devin Mesoraco's 6-4-3 double-play grounder which tied the score.
Chicago began the game on the right foot, as Castro deposited a pitch just over the center-field wall with two down in the first.
LaHair doubled Chicago's advantage in the fourth with a leadoff solo shot to left, and Soto began the fifth with a blast to left for a 3-0 game.
Dempster kept Cincinnati off balance, not allowing a runner past second base for the duration of his outing.
Cincinnati has taken three of five meetings with Chicago this season, and has beaten the Cubs in four of the last five matchups in Ohio...The Cubs also activated reliever Kerry Wood from the 15-day DL, while optioning pitchers Randy Wells and Scott Maine to Triple-A Iowa...Both starters celebrated birthdays on Thursday, with Dempster turning 35 and Bailey turning 26.