Objective: To examine the association between birth weight and non-fatal adult cardiovascular disease while controlling for potential confounders such as socioeconomic group and adult lifestyle. Design: Retrospective self report of birth weight in an ongoing longitudinal cohort of nurses followed up by postal questionnaire every two years. Setting: Nurses' health study, a cohort of 121 700 women followed up since 1976. Main outcome measures: Non-fatal cardiovascular disease, including myocardial infarction, coronary revascularisation, and stroke. Results: Among the 70 297 women free of cardiovascular disease at baseline who reported birth weight in the 1992 questionnaire there were 1309 first cases of non-fatal cardiovascular disease. Increasing birth weight was associated with decreasing risk of non-fatal cardiovascular disease. There were 1216 first cases of non-fatal cardiovascular disease among women who were singletons and had been born full term; their relative risks adjusted for several cardiovascular risk factors were 1.49 (95% confidence interval 1.05 to 2.10) for birth weight 5 lb 8 oz to 7 lb 0 oz); 1.00 (referent) for birth weight >3175-3856 g (>7 lb 0 oz to 8 lb 8 oz); 0.96 (0.80 to 1.15) for birth weight >3856-4536 g (>8 lb 8 oz to 10 lb 0 oz); and 0.68 (0.46 to 1.00) for birth weight >4536 g (>10 lb 0 oz) (P value for trend=0.0004). The inverse trend was apparent for both coronary heart disease and stroke. Conclusions: These data provide strong evidence of an association between birth weight and adult coronary heart disease and stroke. Birth weight and mortality from cardiovascular disease are inversely associated in adult women This study found that birth weight and the risk of non-fatal cardiovascular disease is also inversely associated in adult women for both coronary heart disease and stroke This association is driven by the 13% of women born at the extremes of birth weight It seems to be largely independent of established cardiovascular risk factors also associated with birth weight: adult body weight, hypertension, and diabetes It is not weakened by controlling for childhood socioeconomic group or adjusting for adult lifestyle