60 evaluable patients with prostate cancer currently receiving androgen ablation therapy or who have had an orchiectomy will be enrolled in this study. All patients will be randomized 1:1 (30 patients per treatment arm) to either receive gabapentin or venlafaxine. Treatment duration will be a total of 6 months. During those 6 months, study staff will evaluate frequency and intensity of hot flashes using hot flash score from hot flash diary every 28 days. Patients will also record side effects associated with either gabapentin or venlafaxine on their medication diaries. Study staff will record the severity of all adverse events reported. Patients will also complete the quality of life Functional Assessment of Cancer Therapy-Prostate (FACT-P) form at baseline, cycle 3, and cycle 6/off study.