The role of corticosteroids in the treatment of eosinophilic meningitis has not been definitely established. Patients given a 2-week course of prednisolone (treatment group), 60 mg/day, were compared with those given placebo (control group) in a randomized, double-blind trial. Fifty-five patients were enrolled in each group. There were significant differences between the treatment and control groups, with regard to the number of patients who still had headache after 14 days (5 vs. 25, respectively; P=.00004), the median length of time until complete disappearance of headache (5 vs. 13 days, respectively; P=.00000), and the number of patients who had repeat lumbar puncture (7 vs. 22, respectively; P=.002). Serious side effects were not detected. These results indicate that a 2-week course of prednisolone was beneficial in relieving headache in patients with eosinophilic meningitis.