In a serach for risk factors for myocardial infarction and sudden cardiac death, the mean total vital capacity as measured at multiphasic health checkups was lower in persons who later had a first myocardial infarction than in risk-factor-matched controls (3.17 vs. 3.29 liters, 395 pairs, P less than 0.05) and non-risk-factor-matched controls (3.16 vs. 3.41 liters, 401 pairs, P less than 0.001). Findings were little affected by age and height adjustment and were similar for sudden cardiac death. The first-second vital capacity was also inversely related to later development of these conditions, but the ratio of that measurement to total vital capacity was not. Heavy smoking, productive cough, exertional dyspnea and cardiac enlargement were associated with diminished total capacity. However, exclusion of subjects with these findings did not reduce the predictive value of total vital capacity. Diminished vital capacity deserves continued attention as a possible coronary risk factor. Its relation to subsequent coronary events is not well explained.