Background: Menstrually associated migraine (MAM) is often prolonged and difficult to manage with conventional therapies. Frovatriptan is a new selective 5HTlB/1D receptor agonist indicated for short term management of migraine. It has a long half life and good tolerability. These characteristics suggest that frovatriptan may be useful for the intermittent prevention of MAM. Methods: The study was a randomized, double blind, placebo controlled, three way crossover design. Patients treated each of three perimenstrual periods (PMPs) with placebo, frovatriptan 2.5 mg QD, and frovatriptan 2.5 mg BID. The 6 day treatment started 2 days before the anticipated start of MAM headache. The primary efficacy endpoint was incidence of MAM headache during the 6 day PMP. Results: The population comprised 546 women (mean age, 37.6 years). Use of frovatriptan reduced the occurrence of MAM headache. The incidence of MAM headache during the 6 day PMP was 67% for placebo, 52% for frovatriptan 2.5 mg QD, and 41% for frovatriptan 2.5mg BID. Both frovatriptan regimenswere superior to placebo (p < 0.0001), and the BID regimen was superior to theQD regimen (p < 0.001). Both frovatriptan regimens also reduced MAM severity (p < 0.0001),duration (p < 0.0001),and the use of rescue medication (p < 0.01 QD; p < 0.0001 BID) in a dose dependent manner. The incidence and type of adverse events for both regimens were similar to placebo and consistent with those reported for short term migraine management. Conclusion: Frovatriptan given prophylactically for 6 days was effective in reducing the incidence of menstrually associated migraine. More than half of patients who used frovatriptan 2.5 mg BID had no menstrually associated migraine headache during the 6 day perimenstrual period. The findings are consistent with the long duration of action and good tolerability of frovatriptan observed in short term migraine management. Background: Menstrually associated migraine (MAM) is often prolonged and difficult to manage with conventional therapies. Frovatriptan is a new selective 5HTlB / 1D receptor agonist indicated for short term management of migraine. It has a long half life and good tolerability. These characteristics suggest Methods: The study was a randomized, double blind, placebo controlled, three way crossover design. Patients treated each of three perimenstrual periods (PMPs) with placebo, frovatriptan 2.5 mg QD, and The 6 days treatment started 2 days before the planned start of MAM headache. The primary pharmac endpoint was was MAM headache during the 6 days PMP. Results: The population was 546 women (mean age, 37.6 years). Use of frovatriptan reduced the occurrence of MAM headache. The incidence of MAM headache during the 6 day PMP was 67% for placebo, 52% for frovatriptan 2.5 mg QD, a nd 41% for frovatriptan 2.5 mg BID. Both frovatriptan regimenswere superior to placebo (p <0.0001), and the BID regimen was superior to the QD regimen (p <0.001). Both frovatriptan regimens also reduced MAM severity (p <0.0001), duration (p <0.0001), and the use of rescue medication (p <0.01 QD; p <0.0001 BID) in a dose dependent manner. The incidence and type of adverse events for both regimens were similar to placebo and consistent with those reported for short term migraine management. Conclusion: Frovatriptan given prophylactically for 6 days was effective in reducing the incidence of menstrually associated migraine. More than half of patients who used frovatriptan 2.5 mg BID had no menstrually associated migraine headache during the 6 day perimenstrual period. consistent with the long duration of action and good torability of frovatriptan observed in short term migraine management.