The causes of 50 perinatal deaths which occurred over an 18-year period in the infants of women with either established (n = 205) or gestational (n = 2,442) diabetes were studied. The perinatal mortality rate in these groups was 5.4% and 1.6% respectively and the causes of deaths were similar in both groups. Intrauterine hypoxia was found to be the commonest cause of death, followed by congenital malformations and respiratory distress syndrome. The implications of these findings for measures to reduce such deaths are discussed.