Adjuvant interferon has modest activity in melanoma patients at high risk for relapse. Patient selection is important; stage and ulceration of the primary tumour are key prognostic factors. Methods: In this post hoc meta-analysis of European Organisation for Research and Treatment of Cancer (EORTC) trials 18952 (intermediate doses of interferon alpha-2b [IFN] versus observation in stage IIb-III patients) and 18991 (pegylated [PEG]-IFN versus observation in stage III patients), the predictive value of ulceration on the efficacy of IFN/PEG-IFN with regard to relapse-free survival (RFS), distant metastasis-free survival (DMFS), and overall survival (OS) was assessed in the overall pop Findings: In the overall population, the comparison of IFN/PEG-IFN versus observation for RFS, DMFS and OS yielded estimated hazard ratios (HR) of 0.85 (p = 0.004), 0.89 (p = 0.04) and 0.94 (p = 0.36), respectively. The impact of treatment was greater in the ulcerationgroup (n = 849) compared with the non-ulceration group (n = 1336) for RFS (test for interaction: p = 0.02), DMFS (p < 0.001) and OS (p < 0.001). The greatest risk reductions were observed in patients with ulceration and stage IIb/I Interpretation: This meta-analysis of the EORTC 18952 and 18991 trials indicated that both tumour stage and ulceration were predictive factors for the efficacy of adjuvant IFN/PEG-IFN therapy. (C) 2011 Elsevier Ltd. All rights reserved.