In Crohn's disease, prednisone is believed to be ineffective for relapse prevention. Because all patients with Crohn's Disease Activity Index lower than 150 and with some altered lab tests (erythrocyte sedimentation rate, C-reactive protein, alpha-1 -acid gly coprotein, alpha-1 -acid antitrypsin, and white blood cell count) had a clinical relapse in 18 months of follow-up, we tried to ascertain whether methylprednisolone could reduce the risk of clinical relapse in such patients. Eighteen patients were included in a controlled study against placebo. Nine patients were treated with methylprednisolone at a dosage of 0.25 mg/kg daily for a period of 6 months; treatment was discontinued if disease relapsed or if lab tests were normalized. During the steroid treatment, 1 of 9 patients showed a clinical relapse; in 7, the normalization of lab tests was obtained; in 5 of these 7 patients a relapse occurred within 1 month after the suspension of the treatment; in 1 patient, lab tests remained altered. In those 9 patients on placebo, relapses occurred in 7. We conclude that methylprednisolone was effective in the prevention of relapses for patients in clinical remission but with altered lab tests.