BACKGROUND: Low birth weight is a risk factor for coronary heart disease. It is uncertain how postnatal growth affects disease risk. METHODS: We studied 8760 people born in Helsinki from 1934 through 1944. Childhood growth had been recorded. A total of 357 men and 87 women had been admitted to the hospital with coronary heart disease or had died from the disease. Coronary risk factors were measured in a subset of 2003 people. RESULTS: The mean body size of children who had coronary events as adults was below average at birth. At two years of age the children were thin; subsequently, their body-mass index (BMI) increased relative to that of other children and had reached average values by 11 years of age. In simultaneous regressions, the hazard ratios associated with a 1 SD increase in BMI were 0.76 (95 percent confidence interval, 0.66 to 0.87; P < 0.001) at 2 years and 1.14 (95 percent confidence interval, 1.00 to 1.31; P=0.05) at 11 years among the boys. The corresponding figures for the girls were 0.62 (95 percent confidence interval, 0.46 to 0.82; P=0.001) and 1.35 (95 percent confidence interval, 1.02 to 1.78; P=0.04). Low BMI at 2 years of age and increased BMI from 2 to 11 years of age were also associated with raised fasting insulin concentrations (P < 0.001 for both). CONCLUSIONS: On average, adults who had a coronary event had been small at birth and thin at two years of age and thereafter put on weight rapidly. This pattern of growth during childhood was associated with insulin resistance in later life. The risk of coronary events was more strongly related to the tempo of childhood gain in BMI than to the BMI attained at any particular age. BACKGROUND: Low birth weight is a risk factor for coronary heart disease. It is uncertain how postnatal growth affects disease risk. METHODS: We studied 8760 people born in Helsinki from 1934 through 1944. Childhood growth had been recorded. A total of 357 men and 87 women had been admitted to the hospital with coronary heart disease or had died from the disease. Coronary risk factors were measured in a subset of 2003 people. RESULTS: The mean body size of children who had coronary events as adults was below average at birth . After two years of the children were thin; subsequently, their body-mass index (BMI) increased relative to that of other children and had reached average values ​​by 11 years of age. In simultaneous regressions, the hazard ratio associated with a 1 The corresponding figures for SD were 0.76 (95 percent confidence interval, 0.66 to 0.87; P <0.001) at 2 years and 1.14 (95 percent confidence interval, 1.00 to 1.31; P = 0.05) The girls were 0.62 (95 percent confidence interval, 0.46 to 0.82; P = 0.001) and 1.35 (95 percent confidence interval, 1.02 to 1.78; P = 0.04). Low BMI at 2 years of age and increased BMI from 2 to 11 years of age were also associated with raised fasting insulin concentrations (P <0.001 for both). CONCLUSIONS: On average, adults who had a coronary event had been small at birth and thin at two years of age and thereafter put on weight rapidly. This pattern of growth during childhood was associated with insulin resistance in later life. The risk of coronary events was more strongly related to the tempo of childhood gain in BMI than to the BMI attained at any particular age.