Pirates 1, Cubs 0: A.J. Burnett turned in another strong performance and Rod Barajas hit an RBI single as Pittsburgh handed NL Central rival Chicago its 10th consecutive loss.
Barajas recorded two of the seven hits by the Pirates, who had lost three of four.
Burnett (3-2) limited the Cubs to six hits and two walks with six strikeouts in 5 1/3 innings. The veteran, who improved to 5-0 lifetime against Chicago, has allowed two runs or less in six of his seven starts this season.
Three relievers bridged the gap to Joel Hanrahan, who worked around a pair of hits in the ninth for his 11th save in 12 opportunities.
Pittsburgh gave Burnett all the support he needed in the second inning. Pedro Alvarez led off with a single, moved to second on a one-out groundout and scored on Barajas' line-drive single to right field.
Ryan Dempster (0-3) again was a hard-luck loser, yielding only one run and seven hits in 7 1/3 frames. The right-hander, who saw his career mark against the Pirates fall to 8-13, has surrendered two runs or less in six of his eight outings this year.
Four players had two hits apiece for the Cubs, who have lost 10 in a row for the first time since beginning the 1997 season with 14 straight defeats.
GAME NOTEBOOK: The Pirates designated OF Nate McLouth for assignment prior to Friday's game and recalled IF Matt Hague from Triple-A Indianapolis. McLouth, who spent the first 4 1/2 years of his career with Pittsburgh before being traded to Atlanta in 2009, returned to the Pirates this season and batted just .140 (8-for-57) with two RBIs in 34 games. ... Pittsburgh has scored fewer than two runs 15 times this year. ... Despite losing, Dempster lowered his ERA from 2.28 to 2.14.