The purpose of this study is to evaluate the effectiveness and tolerability (the ability not to experience ill effects from the study drug) of a zolmitriptan nasal spray, 5.0 mg, compared with placebo (inactive drug) for 2 migraine headaches for up to 12 weeks in adult subjects with migraine headaches

Inclusion Criteria:

• Subject has an established diagnosis of migraine headache, with or without aura
• Subject has a medical history indicating the presence of migraine attacks for at least 1 year before the start of the trial or a minimum of 2 and maximum of 6 migraine attacks per month on average for 3 months preceding the study
• Subject has non migraine headaches on fewer than 6 days each month for 3 months preceding the study

Exclusion Criteria:

• Subject has history of basilar, ophthalmoplegic or hemiplegic migraine or serious neurologic condition associated with headache
• Subject has used a MAOI within 2 weeks of randomisation or has been given SSRI therapy or migraine prophylactic agent within 3 months of randomisation. Subject requires treatment with propranolol or cimetidine or has had an intolerable or serious adverse event while using another triptan
• Subject has a history or symptoms suggestive of ischemic heart disease, coronary artery vasospasm or other significant underlying cardiovascular disease or clinically significant abnormalities seen on an ECG or uncontrolled hypertension