OBJECTIVE--To assess the prevalence and patterns of congenital heart defects in infants requiring hospital admission in a defined population and to determine the differences in ethnic groups. DESIGN--A three year retrospective analysis of all hospital admissions for paediatric congenital heart defects in a single centre. SETTING--Tertiary referral centre for infant cardiac services in the West Midlands region, United Kingdom. PATIENTS AND METHODS--Indian, Pakistani, Bangladeshi and other individuals from the Indian subcontinent constitute 5.8% of the total population of the West Midlands region. Some 9% of infants, however, are Asian because of a high birth rate. All infants with confirmed congenital heart defects resident in this region who required hospital admission between April 1990 and March 1993 were classified as Asians and non-Asian, mainly white, infants. RESULTS--Of 1111 infants with congenital heart defects born in the West Midlands and admitted to the hospital, 17.0% were Asian, significantly more than the percentage of Asian infants in the population (P < 0.0001). Asian infants had a higher proportion of complex congenital heart disease (7% v 2.1%, P < 0.001), whereas coarctation of the aorta was more common in non-Asian (3% v 9.1%, P = 0.003). Persistent arterial duct seemed to be more common in Asian children (16% v 10%, NS), but this group included preterm infants admitted for duct ligation. There was no significant difference between the two groups in the other nine categories of congenital heart defects. CONCLUSIONS--The estimated prevalence of congenital heart defects requiring hospital admission was higher in Asian infants than in non-Asian (9.45 per 1000 v 4.56 per 1000, P < 0.0001). Complex congenital heart defects were more common in Asian infants whereas coarctation of the aorta was more common in non-Asian.