The prevalence of cutaneous haemangiomas in a representative population of low birthweight infants was determined by tracing and assessing survivors of pre-school age. Data from hospital case-notes and follow-up assessments were used to investigate whether prevalence of haemangiomas was related to perinatal factors and childhood morbidity. Eleven point one per cent of 615 infants developed a haemangioma. Haemangiomas were more common in girls than boys, and in infants of lower gestational age. Hypothermia in the first hours of life and neonatal illness were associated with lower prevalence, suggesting that neonatal skin perfusion influences haemangioma development; this is consistent with a tendency for haemangiomas to be distributed centripetally. However, the major aetiological determinants are unknown. Children with a haemangioma were more likely to have had a febrile convulsion than those without a haemangioma.