Urinary testosterone and androstanediol were measured by gas chromatography in four groups of premenopausal subjects: 22 healthy women (control group), 21 healthy women with a family history of breast cancer (familiality group), 39 patients with breast lumps which consisted of ductal or lobular hyperplasia (hyperplasia group) and 18 patients with infiltrating breast carcinoma (carcinoma group). On the basis of normal values found in our laboratory, steroid levels were above normal in 4.5% of the controls, 4.7% of the familiality group, 38.5% of the hyperplasia group (P less than 0.01 vs controls) and 61.1% of the carcinoma group (P less than 0.001 vs control group). The mean testosterone level in the carcinoma group (11.3 +/- 6.78 S.D.) and the mean androstanediol level in the hyperplasia group (47.25 +/- 31.0 S.D.) were significantly higher than those of the control group (testosterone 6.25 +/- 3.48 S.D., androstanediol 32.55 +/- 20.0 S.D.). No significant difference was found in mean testosterone or androstanediol levels between the control group and the familiality group (testerone 5.41 +/- 3.6 S.D., androstanediol 29.38 +/- 15.89 S.D.). We conclude that increased excretion of androgenic steroids is a hormonal abnormality common to breast cancer patients and to patients with breast epithelial hyperplasia, but not to subjects with a family history of carcinoma of the breast.