A systematic review including 7 studies with a total of 738 subjects was abstracted in DARE. The patients had acute severe migraine headache. The addition of i.m. or i.v. dexamethasone at doses of 10, 15, 20 or 24 mg to standard abortive care (numerous cointerventions were used) reduced the recurrence of migraine 24 to 72 h after treatment compared with placebo (RR 0.74, 95% CI 0.60 to 0.90) but did not influence initial headache pain reduction (4 studies, n=455, 95% CI –0.20 to 0.94). For the outcome of recurrent migraine, no significant differences were found between i.m. and i.v. administration of dexamethasone. Patients treated with dexamethasone were more likely to have dizziness (6 studies, n=626, RR 2.15, 95% CI 0.98 to 4.74), but less likely to have other adverse events (RR 0.50, 95% CI 0.30 to 0.82).