Clinical and laboratory data on infectious complications in 100 consecutive heart transplant recipients were analyzed retrospectively. The mean length of follow-up was 651 +/- 466 days. All patients received a basic immunosuppressive regimen including cyclosporine (whole blood target trough level 400-600 micrograms/l), azathioprine (1 mg/kg/day) and prednisone (0.15 mg/kg/day). Early rejection prophylaxis consisted of polyclonal rabbit antithymocyte globulin (ATG) (4 mg/kg/day for 4 days) in the first 57 patients and monoclonal murine OKT-3 (5 mg/day for 14 days) in the remaining patients. The primary cause of death was infection in three patients and rejection in 16 (p < 0.001). The incidence of infection was 0.96/patient/year (n = 179); 95 infections were nosocomial (53%), 47 community-acquired (26%) and 37 opportunistic (21%). The number of hospitalizations due to infections was fewer than that due to rejection (53 versus 246 respectively, p < 0.0001), but the mean length of hospital stay was longer in the first group (13.85 +/- 10.92 days versus 3.48 +/- 2.28 days, p < 0.001). Previous early rejection prophylaxis with OKT-3 was associated with a greater number of opportunistic and nosocomial infections compared to prophylaxis with ATG (p < 0.05), as was treatment with ATG and steroid pulses compared to steroid pulses alone in cases of opportunistic infection (p < 0.05).