Breast cancer and endometrial cancer share several risk factors, including age, obesity and higher endogenous estrogen levels. As a result, these two cancers may be amenable to common risk reduction strategies. This possibility was evaluated in studies undertaken in the Women’s Health Initiative (WHI) cohort and in the Kaiser Permanente Southern California (KPSC) integrated health plan. In the WHI Observational Study, intentional weight loss was associated with a significant reduction in endometrial cancer risk (hazard ratio [HR] 0.60, 95% confidence interval [CI] 0.42–0.86). In the KPSC cohort of women with breast cancer, as might be expected given the known risk profile of tamoxifen, aromatase inhibitor use was associated with significantly lower endometrial cancer risk compared to tamoxifen use (HR 0.52, 95% CI 0.31–0.87). Compared to the no endocrine therapy group, aromatase inhibitor users had a trend towards fewer endometrial cancers (HR 0.71, 95% CI 0.37–1.35). As the aromatase inhibitors exemestane and anastrozole have been demonstrated to reduce breast cancer incidence in full scale primary prevention trials, findings from the studies outlined in this review suggest two potential strategies for reducing both breast cancer and endometrial cancer risk, especially in overweight and obese women who are most likely to develop these diseases.