Risk of coronary heart disease (CHD) among the Honolulu Heart Program participants was examined in relation to body mass index (BMI) at age 25 and two subsequent periods of weight change: age 25 to examination I (1965-1968) and examination I to examination III (1971-1974). During a maximum follow-up period of 17 years after examination III, there were 479 incident cases of CHD among the study sample of 6,176 Japanese-American men. Levels of BMI at age 25 were positively related to CHD incidence after statistical control for age, smoking, and subsequent weight change. Relative risk between the lowest and highest BMI categories was 2.44 (95% confidence interval (CI) 1.61-3.69). Compared with a weight change of less than 2.5 kg between age 25 and examination I, relative risks were 1.41 (95% CI 1.00-1.97) for a weight gain between 2.6 and 5 kg, 1.60 (95% CI 1.22-2.11) for a weight gain between 5.1 and 10 kg, and 1.75 (95% CI 1.32-2.33) for a weight gain of more than 10 kg. During the examination I-III period, in contrast, the highest risk of CHD was found in men who lost the greatest amount of weight; the relative risk of CHD for men who lost more than 2.5 kg was 1.25 (95% CI 0.98-1.60). The authors conclude that levels of relative weight in early adulthood were positively related to risk of CHD occurring much later in the lives of these men. The association between CHD incidence and weight change appeared to be modified by age, with higher risks for earlier weight gain and later weight loss in the lives of these men.