Physical activity at work and in leisure time was studied by using a questionnaire in a random population sample from two counties of Eastern Finland in 1972. Data on age, serum cholesterol, diastolic blood pressure, height, weight and smoking were recorded in a field examination. The study population consisted of 3978 men aged 30-59 years and 3688 women aged 35-59 years. The participation rate was 92% in men and 94% in women in these age groups. During the approximately seven-year follow-up until December 31, 1978, 210 men and 63 women had an acute myocardial infarction (AMI), 89 men and 14 women died of acute ischemic heart disease, 71 men and 56 women had a cerebral stroke and 172 men and 75 women died of any disease. The subjects with a history of myocardial infarction, angina or cerebral stroke in the 12 months preceding the baseline survey were excluded in the respective analysis. Low physical activity at work was associated with an increased risk of AMI, cerebral stroke and death due to any disease in both men and women, even when controlling for age, serum total cholesterol, diastolic blood pressure, height, weight and smoking in a multiple logistic model. The relative risk of AMI was 1.5 (90% confidence interval (CI) = 1.2-2.0) in men and 2.4 (90% CI = 1.5-3.7) in women. Low physical activity in leisure time had a significant association with an increased risk of death, but not with an increased risk of AMI or stroke in the multivariate analysis.