Some 43 of 60 (72%) renal allograft recipients who were prospectively randomized to receive either OKT3 monoclonal antibody (n = 30) or ALG (antilymphocyte globulin) polyclonal antibody (n = 30) for steroid-resistant rejection suffered from infection, 25 (83%) following OKT3 and 18 (60%) following ALG treatment (P < 0.05). Clinically evident herpes infection was most frequently seen (9 and 7, respectively), followed by pneumonia (6 and 1, respectively P < 0.05), urinary tract infection and wound infection (2 of each in both groups) fungal (Candida) and multibacterial infections. One patient died in each group due to cytomegalovirus (CMV) pneumonia, giving a mortality of 4.3% in each group. Actuarial 1-year graft and patient survival rates were 80% and 97% in both groups, respectively. It is concluded that ALG and OKT3 are equally effective in renal allograft rejection resistant to steroid treatment, however, the risk of infection appears to be higher with OKT3.