Endogenous sex hormones are thought to be involved in breast and endometrial cancers, but few studies have evaluated the relationships between hormones and risk factors for these diseases.We related serum hormone and sex-hormone binding globulin (SHBG) levels to reproductive and lifestyle risk factors in a cross-sectional study of 125 postmenopausal women in five geographic regions of the United States.The estrogens were associated positively, while SHBG was associated negatively with body mass index (wt/ht2). Estrone, (E1), estrone sulfate, and bioavailable estradiol (BioE2) were inversely associated with height. Androstenedione was positively associated with age at menopause, while androstenedione, E1, estradiol, and BioE2 were inversely associated with age at menarche. Weekly alcohol drinkers had higher hormone levels, and lower SHBG levels than those who abstained. Androstenedione and E1 decreased with increasing levels of nonrecreational activity.Several of these findings support the hypothesis that breast and endometrial cancer risk factors are mediated, in part, through increased endogenous hormone levels. The androstenedione findings are of interest in light of studies relating androstenedione to endometrial and possibly breast cancer. An association of age at menarche with E2, independent of androstenedione, may reflect increased aromatase activity in women with earlier menarche.