During the year 1983, 170 patients underwent open heart surgery; coronary bypass surgery in 50, valve replacement in 69, valve repair in 9 and congenital heart surgery in 47. Sternal wound infection was seen in 14 patients: 10 (5.8%) patients had minor infection, recovered with extended antibiotic therapy and local hygiene, and 4 (2.3%) patients had major wound infection which required debridement and resuturing of the wound, prolonged antibiotic treatment and hospitalization. However no one developed costochondral infection. Sternal wound infection was 6 times higher among coronary bypass patients (20%) than among patients with other types of open heart surgery (3.3%). Leg wound infection was observed in 7 (14%) patients, all minor. The prevalence of diabetics was 54% among coronary-bypass patients and 6.5% among non-coronary group. Wound infection was three times higher in diabetic--or obese patients than among non diabetic--or non obese patients. Infections were not related to age, sex, smoking habits or social class. The interval between catheterisation and operation, the preoperative stay in hospital, preoperative haemoglobin or albumin level, and the time during which the patient was on the ventilator and re-opening the chest for bleeding had no influence. A significantly higher incidence of infection in patients undergoing coronary artery surgery in addition to high prevalence of diabetic or obese patients was related to the longer duration of operation procedure and the coronary perfusion time.