Although perfusion of infants and small children is similar in many ways to perfusion of older patients, the small size of these patients introduces several factors which are dangerous for the patient and challenge the surgical team. It is apparent that perfusion can be performed on even the smallest infants. It is equally certain that present methods of perfusion in small infants are hazardous and should be applied only in extraordinary circumstances. Certainly, much needs to be learned before these methods become elective. The purpose of this presentation is to review our experiences with open-heart surgery in small children in order to elucidate some of the problems encountered. Seventy patients with body surface area (BSA) of 0.5 sq m or less were perfused. Not all of these were infants. Some were older children whose growth was impaired because of their congenital heart disease. The problems of extracorporeal circulation were similar,