Sixty-six consecutive biopsies of renal allograft recipients treated with OKT3 monoclonal antibody were reviewed and placed into one of two groups. Group I (29 patients) had evidence of acute vascular and cellular rejection, while group II (32 patients) had cellular rejection but no vascular rejection. In 5 cases, the sample was inadequate to determine if vascular rejection was present or not. The severity of the cellular rejection was graded histologically as mild, moderate, or severe. The severity was equivalent when comparing group I with group II (mild, 17% vs. 10%; moderate, 52% vs. 59%; and severe, 31% vs. 31%). There was no difference in the rejection reversal rate between the two groups (86% vs. 91%). However, at 6 and 12 months there was a higher graft loss in the group with vascular rejection (graft survival 64% vs. 81%, P = 0.13, and 58% vs. 75%, P = 0.08, respectively). The poorest outcome was in those patients with both severe acute cellular rejection and acute vascular rejection (4/9, or 44%). The serum creatinine level was higher both pre- and post-OKT3 therapy and at 1, 6, and 12 months in the group with vascular rejection. In conclusion, OKT3 was equally successful in reversing acute cellular rejection and acute vascular rejection. However, increased graft loss occurred at 6 and 12 months in the group with vascular rejection.