The relationship between sex hormones and high-density lipoprotein cholesterol levels in healthy adult men. The objective of this study was to clarify the complex and uncertain relationship between endogenous sex hormones and high-density lipoprotein (HDL) cholesterol levels in healthy men. Fifty-five healthy adult men were consecutively recruited from an ongoing cross-sectional study of cardiovascular disease risk factors from a lipid research clinic at the University of Washington, Seattle. Subjects receiving medication were excluded. Multiple linear regression analysis identified several factors that correlated highly significantly with HDL cholesterol levels, including alcohol intake; frequency of strenuous exercise; age; levels of total cholesterol, low-density lipoprotein cholesterol, and triglyceride; and carbohydrate intake. Nearly 80% of the heterogeneity in HDL cholesterol levels could be accounted for by these factors. Despite finding significant correlations with factors known to influence HDL cholesterol levels, no correlation with estradiol level, testosterone level, or the ratio of estradiol to testosterone levels was apparent. In conclusion, endogenous sex hormones do not appear to influence HDL cholesterol levels in healthy adult men. Alternatively, a large proportion of the heterogeneity in HDL levels in this group of men can be accounted for by environmental factors. The disparity between this conclusion and others may be partially due to differences in accounting for these confounding variables. 