Migraine is a common, disabling condition and a burden for the individual, health services, and society. Zolmitriptan is an abortive medication for migraine attacks, belonging to the triptan family. These medicines work in a different way to analgesics such as paracetamol and ibuprofen. To determine the efficacy and tolerability of zolmitriptan compared to placebo and other active interventions in the treatment of acute migraine attacks in adults. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, and the Oxford Pain Relief Database, together with three online databases (www.astrazenecaclinicaltrials.com, www.clinicaltrials.gov, and apps.who.int/trialsearch) for studies to 12 March 2014. We also searched the reference lists of included studies and relevant reviews. We included randomised, double-blind, placebo- or active-controlled studies, with at least 10 participants per treatment arm, using zolmitriptan to treat a migraine headache episode. Two review authors independently assessed trial quality and extracted data. We used numbers of participants achieving each outcome to calculate risk ratios and numbers needed to treat for an additional beneficial effect (NNT) or harmful effect (NNH) compared with placebo or a different active treatment. Twenty-five studies (20,162 participants) compared zolmitriptan with placebo or an active comparator. The evidence from placebo-controlled studies was of high quality for all outcomes except 24 hour outcomes and serious adverse events where only limited data were available. The majority of included studies were at a low risk of performance, detection and attrition biases, but did not adequately describe methods of randomisation and concealment.Most of the data were for the 2.5 mg and 5 mg doses compared with placebo, for treatment of moderate to severe pain. For all efficacy outcomes, zolmitriptan surpassed placebo. For oral zolmitriptan 2.5 mg versus placebo, the NNTs were 5.0, 3.2, 7.7, and 4.1 for pain-free at two hours, headache relief at two hours, sustained pain-free during the 24 hours postdose, and sustained headache relief during the 24 hours postdose, respectively. Results for the oral 5 mg dose were similar to the 2.5 mg dose, while zolmitriptan 10 mg was significantly more effective than 5 mg for pain-free and headache relief at two hours. For headache relief at one and two hours and sustained headache relief during the 24 hours postdose, but not pain-free at two hours, zolmitriptan 5 mg nasal spray was significantly more effective than the 5 mg oral tablet.For the most part, adverse events were transient and mild and were more common with zolmitriptan than placebo, with a clear dose response relationship (1 mg to 10 mg).High quality evidence from two studies showed that oral zolmitriptan 2.5 mg and 5 mg provided headache relief at two hours to the same proportion of people as oral sumatriptan 50 mg (66%, 67%, and 68% respectively), although not necessarily the same individuals. There was no significant difference in numbers experiencing adverse events. Single studies reported on other active treatment comparisons but are not described further because of the small amount of data. Zolmitriptan is effective as an abortive treatment for migraine attacks for some people, but is associated with increased adverse events compared to placebo. Zolmitriptan 2.5 mg and 5 mg benefited the same proportion of people as sumatriptan 50 mg, although not necessarily the same individuals, for headache relief at two hours.