To explore the relation between environmental influences in early life and risk of cardiovascular disease in adulthood, case-control comparisons were made on 99 patients with acute myocardial infarction and 55 patients with recent hemisphere stroke. After allowance for smoking habits and current social class, risk of myocardial infarction was higher in subjects of lower social class at birth, smaller stature, and with a history of infant and especially perinatal death in a sibling. Stroke was also associated with infant or perinatal death in a sibling. Although none of these associations was statistically significant at a 5% level, they support other evidence that implicates the pre and early postnatal environment in the aetiology of cardiovascular disease.