AB - Urinary excretion of 17 ketosteroids (17KS), 17 ketogenic steroids (17KGS), and creatinine was measured in a cohort of 162 females between the ages of 35 and 45. Height and weight were also measured. A second group of women consisting of all those over 20 years of age, over 165 pounds (75 kg) in weight, and who had measurements of urinary 17KS excretion were selected from laboratory records. A third group of women who met all the criteria for the obese group, except that they weighed less than 165 pounds, were selected from the same hospital records. In the first group none of the parameters of body mass correlated with 17KS or 17KGS excretion either alone or combined in multiple or partial correlations. Likewise, none of the parameters of body mass in the obese group were correlated with 17KS or 17KGS excretion. Age was negatively correlated with 17KS excretion in this group and mean 17KGS excretion was significantly greater. Mean 17KS and 17KGS excretions in the third group of nonobese hospitalized women were not significantly different from the means in the first group. It is concluded that body mass has no influence on 17KS excretion in normal women and that a variable associated with increased body weight, but not weight itself, is responsible for increased urinary excretion of 17KGS in obese women.