In Chicago, Larry Bird scored 24 points and Cedric Maxwell had 19 as Boston took a 3-0 lead in its Eastern Conference semifinal playoff series.
The Celtics, who had the best record in the NBA during the regular season, can advance to the conference final by beating Chicago Sunday.
Boston scored six straight points in the opening three minutes of the fourth quarter, four by Maxwell and two by Bird, to take a 93-87 lead. Chicago closed within two points on two occasions but could not overtake Boston.
Bird scored 14 of his points in the second half, inlcuding 10 in the third quarter when Boston rallied from a 60-57 halftime deficit to take an 87-85 lead entering the final quarter. Robert Parish and Nate Archibald had 16 each and Kevin McHale came off the bench to score 13 for the Celtics.
David Greenwood scored 23 points and Reggie Theus had 26 for Chicago.
The Celtics, behind three three-point goals by Chris Ford, took a 31-29 lead late in the first quarter.
The Celtics got their running game in gear in the second quarter, opening up a 47-42 lead behind McHale. Chicago scored six straight points to regain the lead with 4:51 left in the half.