The contribution, by peripheral conversion, of androstenedione and testosterone to the circulating estrogens was determined in men with cirrhosis of the liver. The conversion ratio of androstenedione to estrone, estradiol and testosterone and the conversion ratio of testosterone to estrone (but not estradiol) and androstenedione were significantly increased. The plasma concentrations of androstenedione and testosterone were increased and decreased respectively; the mean plasma concentration of androstenedione being similar to that found in normal women. The metabolic clearance rate of androstenedione was not altered in cirrhosis although the metabolic clearance rate of testosterone was decreased. The production rate of androstenedione was elevated while that of testosterone was reduced. The instantaneous contribution of plasma androstenedione to estrone and estradiol was increased in cirrhosis as was the contribution of testosterone to estrone (but not to estradiol). Thus the increased estradiol levels in cirrhosis result, in large part, from increased peripheral conversion from the androgens. The percent contribution of plasma testosterone to plasma androstenedione was decreased although the absolute amount derived by conversion was normal. The percent contribution of plasma androstenedione to plasma testosterone was increased sevenfold in cirrhosis. The fraction of the daily androstenedione production derived from the plasma testosterone pool was not significantly altered. However, a significant fraction of the daily production rate of testosterone was derived from androstenedione. Thus, 15% of the circulating testosterone is not secreted but is derived by peripheral conversion from androstenedione. Normal levels of gonadotropins were found in cirrhosis.