In this pilot study, 22 women with breast cancer on tamoxifen therapy with at least two hot flashes a day took oral gabapentin at 300 mg three times a day for 4 weeks. The 16 women who completed the study had a mean decrease in hot flash duration of 73.6% (P = 0.027), frequency of 44.2% (P < 0.001), and severity of 52.6% (P < 0.001), with a complete response in 8/16 women. Side effects reported by four women who did not complete 4 weeks of the study were nausea (1/4), rash (1/4) and excessive sleepiness (3/4). Two additional patients did not provide complete data. Gabapentin is a promising new agent in the treatment of tamoxifen induced hot flashes, and should be studied further.