Aim: To evaluate CDP571, a humanized monoclonal antibody to tumour necrosis factor-α, for the treatment of corticosteroid-dependent Crohn's disease. Methods: Patients with corticosteroid-dependent Crohn's disease (use of prednisolone 15-40 mg/day or budesonide 9 mg/day for at least 8 weeks, a previous failed attempt to discontinue corticosteroids within 8 weeks, and Crohn's Disease Activity Index score 150 points or less) were enrolled in a 16-week, randomized, double-blind, placebo-controlled trial. The patients received intravenous CDP571 (20 mg/kg at week 0 and 10 mg/kg at week 8) or placebo. Corticosteroid therapy was decreased following a predefined schedule. The primary efficacy end-point was the percentage of patients with corticosteroid-sparing [i.e. no disease flare (Crohn's Disease Activity Index score ≥220 points) and no longer requiring corticosteroid therapy] at week 10. The major secondary efficacy end-point was corticosteroid-sparing at week 16. Results: Seventy-one patients received treatment. Corticosteroid-sparing was achieved by 19 of 39 (48.7%) CDP571 patients and 13 of 42 (40.6%) placebo patients (P = 0.452) at week 10, and by 18 of 39 (46.2%) CDP571 patients and seven of 32 (21.9%) placebo patients (P = 0.032) at week 16. CDP571 therapy was well-tolerated and the incidence of serious adverse events was similar to placebo. Conclusions: The CDP571 was effective for corticosteroid-sparing at week 16 but not week 10, and was well-tolerated in patients with corticosteroid-dependent Crohn's disease. © 2005 Blackwell Publishing Ltd.