To determine the effect of estrogen on weight changes in women, eight adult females were followed for a period of six months subsequent to hysterectomy or ovariohysterectomy. Three groups comprised the study: 1) a hysterectomy or control group, 2) an ovariohysterectomy group with estrogen replacement therapy, and 3) an ovariohysterectomy without estrogen treatment group. Body weight, caloric intake, and activity level were recorded for the eight prospective subjects over the six month period. Weight data were gathered from past medical records on an additional 19 patients meeting the treatment criteria. Weight changes between groups were not statistically significant. A trend in weight changes among the groups was noted. The hysterectomy group lost five pounds, ovariohysterectomy treated group lost one pound and the untreated group, 0.2 pound. The same trend in weight changes was noted when data from prospective and retrospective subjects were combined. Caloric intake and activity levels did not explain all changes noted. Detailed information on subjects was presented as case studies. The results supported the concept that endogenous estrogen protects against weight gain; evidence did not support the comparable action of exogenous estrogen. Subjects having ovariohysterectomy stated that they experienced appetite changes such as cravings for sweets, undesirable muscle tone and body contour changes, and difficulty in ability to control weight. Further research with a larger sample size is needed to determine direct relationships between female hormones and suppression of weight gain in women.