The perinatal outcome and congenital malformations in children born between 1978 and 1987 in Great Britain after in-vitro fertilization (IVF) at Bourn Hall Clinic and the Hallam Medical Centre are presented. The average maternal age was 34.2 years. Multiple births were frequent, constituting 23% of all deliveries; 19% were twins and 4% triplets. There were no quadruplet or higher order multiple births during that period. Twenty-five per cent of all deliveries were preterm. The mean birth weight was 2793 g and was strongly related to multiplicity of pregnancy and gestational age. Overall, 32% of babies had a low birthweight (less than 2500 g) with 6% having a very low birthweight (less than 1500 g). The overall stillbirth and infant mortality rates were two to three times higher than those of infants born after natural conception in England and Wales; this is attributed to the high incidence of multiple births. The stillbirth rates were 5.07, 20.8 and 24.7 per thousand total births in singletons, twins and triplets respectively. The corresponding figures for perinatal mortality were 13.5, 38.2 and 37 per thousand. Overall, 2.5% of the babies had one or more major congenital malformations diagnosed within one week of life. This was within the range of expected values in the United Kingdom and there was no significant increase in any specific malformation.