Currently, there are no data available on long-term effects of angiotensin-converting enzyme inhibitors (ACE-I) on graft function in children after renal transplantation. We therefore analyzed all children who were transplanted at our institution between 1989 and 1998 and followed for at least 2 years. Those treated with ACE-I, mainly because of failure of other antihypertensive medications, were compared to those without ACE-I. The ACE-I-treated children ( n=19) showed significantly better blood pressure control during the 1st year of follow-up ( p<0.05). In children with chronic allograft dysfunction ( n=8), treatment with ACE-I stabilized graft function, with improvement in creatinine clearance in 50% ( p<0.01). Serum potassium and hemoglobin levels remained stable. One patient discontinued ACE-I because of renal artery stenosis. Taken together, ACE-I were effective and safe in the treatment of hypertension in children following renal transplantation. Children with chronic allograft dysfunction experienced a stabilizing effect on graft function.