Between 1980 and 1987, 31 cases of osteitis (n = 9) and/or mediastinitis (n = 22) were observed after 2,801 consecutive aorto-coronary bypasses (1.1%). Three types of treatment were used: 1) sternal debridement with osteosynthesis and continuous mediastinal irrigation (n = 25); 2) sternal and mediastinal debridement with open drainage without osteosynthesis (n = 2); 3) incision and debridement of sternal abscesses (n = 4). The overall mortality was 26% (8/31), i.e. 11% (1/9) for isolated osteitis and 32% (7/22) for mediastinitis. Four factors were statistically associated with infection: reoperation for hemorrhage (19.4%, p less than 0.001); preoperative diabetes (25%, p less than 0.001), postoperative low cardiac output (55%, p less than 0.001), postoperative respiratory insufficiency (45%, p less than 0.001).