3. To objectively measure hot flashes at baseline and monitor changes in hot flashes after one, three, six and 12 months of letrozole or exemestane therapy, and correlate these changes with serum FSH and LH concentrations. We will test the hypothesis that aromatase or estrogen receptor variants influence the phenotype of hot flashes at baseline or during treatment as part of a broader approach in which we will test for associations with other candidate genes involved in estrogen metabolism and signaling, or with aromatase inhibitor metabolism and disposition.