Use of phototherapy for hyperbilirubinaemia in 300 consecutively treated infants has shown that minor complications are common. With a knowledge of these complications and measures taken to minimize their effects, phototherapy appears to be safe in the short term. The long-term follow-up study showed that growth, and in particular head circumference, was not affected. There was, however, a higher incidence of squints and abnormal developmental performance in those infants treated with phototherapy. This may not have been due to phototherapy usage per se. However, because of these findings, it is suggested that phototherapy should not be used indiscriminately for hyperbilirubinaemia until the results of further long-term studies are available.