We investigated differences in resting metabolic rate (RMR) and cardiovascular disease risk factors among 86 middle-aged men (36 to 59 years) classified as resistance-trained ([RT] n = 19), aerobic-trained ([AT] n = 37), or untrained ([UT], n = 30) according to habitual exercise patterns. RMR, body composition, body fat distribution, supine blood pressure, maximal aerobic capacity (VO2max), plasma lipid levels, and fasting levels of insulin, glucose, and thyroid hormones were measured. We found that RMR, adjusted for differences in fat-free mass, showed a tendency to be greater in AT men as compared with RT men (P = .09) and was greater in AT men as compared with UT men (P < .05). No differences in RMR were noted between RT and UT men. UT men had higher values for total cholesterol, triglycerides, low-density lipoprotein cholesterol (LDL-C), and the insulin to glucose ratio and lower values for high-density lipoprotein cholesterol (HDL-C) (all P < .01) as compared with RT and AT men, whereas no differences in these variables were noted between RT and AT men. Supine diastolic blood pressure was lower in RT men as compared with both AT and UT men. Stepwise regression analysis showed that variations in body fatness accounted for the greatest variation in fasting lipid profile, blood pressure, and the insulin to glucose ratio among groups.(ABSTRACT TRUNCATED AT 250 WORDS)