We have determined the levels of serum sex hormones, the binding capacity of sex hormone binding globulin (SHBG), urinary estrogens, serum lipids, lipoproteins, and apolipoproteins A-I, A-II, and B in 30 healthy middle-aged Finnish men with similar dietary habits. Serum levels of total testosterone, free testosterone, 5 alpha-dihydrotestosterone (5 alpha-DHT), and the binding capacity of SHBG were all positively correlated to high density lipoprotein cholesterol (HDL-C) and apolipoprotein A-I (apo A-I) (r = .43 to .80, P less than 0.05 to 0.001). Total testosterone and 5 alpha-DHT showed a positive correlation to the ratio of apo A-I to Apo A-II (r = .37, P less than 0.05 and r = .58, P less than 0.01, respectively). Serum estradiol levels were negatively correlated to serum total cholesterol, low density lipoprotein cholesterol (LDL), and Apo B (r = -.51 to -.56, P less than 0.01). Moreover, serum free estradiol was negatively correlated to HDL-C and Apo A-I (r = -.46 and r = -.50, P less than 0.01). In multiple linear regression analysis, 5 alpha-DHT was the most significant independent determinant of HDL-C and apo A-I levels when androgens, luteinizing hormone, estradiol, binding capacity of SHBG, and exogenous factors such as age, body mass index (BMI), smoking, alcohol consumption, and diet were taken into account. Multivariate analysis also demonstrated that both total and free estradiol were inversely related to serum Apo B levels.(ABSTRACT TRUNCATED AT 250 WORDS)