The authors evaluated the efficacy of antithymocyte globulin (ATG) induction and delayed initiation of cyclosporine (CsA) in heart transplant (HTx) patients with postoperative renal dysfunction (RD). The authors compared 15 adult HTx patients with postoperative RD (serum creatinine [SCr] > or =150 microM) to 17 controls without postoperative RD. ATG was given daily (1.5 mg/kg/day for 5 days) in controls and every 2 to 5 days in RD patients (total lymphocyte count <200/mm). All patients received corticosteroids and mycophenolate mofetil. The initiation of CsA was delayed in RD patients until SCr had decreased to less than 150 microM (day 12 +/- 8 vs. 2 +/- 1, P<0.0001). One-year patient survival and acute rejection rates were 87% and 27% in RD patients and 88% and 59% in controls, respectively (P=not significant). SCr improved in RD patients and did not differ from controls after the first month. The authors' results suggest that marked prolongation of the period of ATG induction permits a safe delay in the initiation of CsA in HTx patients with postoperative RD.