Renal function was monitored in eight children who were long-term survivors of heart transplantation and who were treated with cyclosporine. Both creatinine clearance and true glomerular filtration rate remained normal 17 to 69 months after transplantation. The survival rate was 80% at 6, 12, and 24 months, and the rejection rate in survivors was only 0.37. Thus adequacy of renal function can be preserved, without jeopardizing overall transplant results, by using small doses of cyclosporine.