The use of angiotensin-converting enzyme (ACE) inhibitors in pregnancy has been associated with neonatal morbidity and mortality. The mechanism of renal dysfunction likely is related to fetal hypotension and prolonged decreased glomerular filtration. Six of 14 previously published cases of neonatal renal failure after maternal ACE inhibitor therapy resulted in death. Eight infants survived after peritoneal dialysis, some with residual renal impairment. Serum lisinopril levels and ACE activity in our patient indicate that during the anuric state the drug has an extremely prolonged half-life, and that it is removed by peritoneal dialysis. In view of this prolonged half-life and the drug's continued suppression of ACE activity and renal function, we recommend institution of early dialysis in infants with renal failure after maternal therapy with lisinopril.