The relation of habitual physical activity to various components of health-related fitness as well as the 12-month repeatability of the measurements were investigated in middle-aged men. Physical activity was assessed by 7-d recall interview. In the men with cardiopulmonary or musculoskeletal diseases total energy expenditure (TEE) correlated directly with maximal oxygen uptake (VO2max) and inversely with the sum of skinfolds, serum triglycerides, and plasma fibrinogen. Energy expenditure at rest (REE) associated inversely to VO2max and directly to skinfolds. In the healthy men REE correlated inversely with VO2max and HDL-cholesterol, and directly with skinfolds. TEE correlated directly with skinfolds but was not associated with VO2max. The associations were similar at both examinations. Correlation coefficients between baseline and follow-up examinations of TEE, REE, VO2max, and sum of skinfolds were 0.60, 0.84, 0.88, and 0.87 for the diseased men, and 0.52, 0.70, 0.86, and 0.91 for the healthy men, respectively (P < 0.001). Habitual physical activity associate beneficially to cardiorespiratory fitness, body fatness and CHD risk factors, essential components of health-related fitness, in middle-aged men with chronic diseases.