AIMS: To study the association of size at birth and social circumstances at birth with 28 day case fatality of acute myocardial infarction (AMI). METHODS: Based on 1,776 first cases of AMI occurring in Uppsala Birth Cohort (men and women born 1915-1929) between 1964 and 2002. Data on circumstances at birth retrieved from archived obstetric records; data on social characteristics in adulthood, hospitalizations, and date of death obtained through linkage to Censuses, Hospital Discharge Register, and Cause of Death Register. RESULTS: We found a U-shaped association between standardized birth weight and case fatality of AMI in men (p = 0.045 for age and period adjusted quadratic trend over quintiles of standardized birth weight) that was driven by cases of AMI occurring during the early years of follow-up. We found no association between standardized birth weight and case fatality of AMI in women. There was a statistically non-significant inverse association of AMI case fatality with social class at birth as well as with social class and household income in adulthood in the cohort. Marital status was a strong determinant of case fatality in men. CONCLUSIONS: Standardized birth weight for gestational age was associated with case fatality of AMI in men. Social class at birth was weakly inversely associated with case fatality of AMI in the cohort.