Follow-up studies were conducted to assess the medical and developmental outcome of 92 infants treated with extracorporeal membrane oxygenation at the University of Michigan. Of 118 near-term (greater than 34 weeks' gestation) infants who received extracorporeal membrane oxygenation, 103 (87%) were surviving and available for follow-up at between 1 and 7 years of age. Ninety-two of these children were seen on at least one occasion. Each visit included a history and physical examination, an evaluation by a physical therapist, and developmental testing by a pediatric psychologist. Medical outcome during year 1 found 31% of the children rehospitalized, primarily with respiratory illness. Outpatient-treated lower respiratory tract illness was seen in an additional 31% of the children. New or nonstatic neurologic problems were noted in 6% of the children. Abnormal growth during year 1 occurred in 26% of the children. At last clinic visit 16% of the children exhibited moderate-to-severe neurologic abnormalities, and 8% had moderate-to-severe cognitive delay. Sensorineural hearing loss occurred in 4% of children. Nine percent of the children were receiving speech and language therapy; screening tests showed that an additional 6% had speech and language delay. Overall, at last visit 16 (20%) of the children exhibited some type of handicap. A review of the literature on follow-up studies of non-extracorporeal membrane oxygenation-treated infants with persistent pulmonary artery hypertension produced an impairment rate of 18.5%. Outcome post-extracorporeal membrane oxygenation appears similar to that seen in less ill cohorts of infants treated with more "conventional" therapy. Long-term follow-up of all such infants remains essential.