Last year the Melanoma Group of the European Organization for Research and Treatment of Cancer (EORTC-MG) completed accrual (1418 patients) for trial EORTC 18952, a three-arm phase III trial evaluating adjuvant therapy with two different intermediate doses of interferon (IFN) alfa-2b versus observation for stage IIB-III melanoma. About 25% of the patients entered the trial with tumor-positive sentinel nodes (SNs). Prognosis was significantly better in SN-positive patients than in patients with palpable regional node involvement (P < .00001). Subsequently the EORTC-MG embarked on two large phase III trials of adjuvant therapy based on the tumor status of the SN. In trial EORTC 18961 for stage II melanoma, GM2-KLH/QS-21 vaccination is compared with observation (1300 patients); in trial EORTC 18991 for stage III melanoma, 5-year treatment with pegylated interferon alfa-2b (PEG-Intron) is compared with observation (900 patients). Translational research projects will compare SN assessment by hematoxylin and eosin (H&E) staining, immunohistochemistry (IHC), and reverse transcriptase-polymerase chain reaction (RT-PCR) to determine the relative accuracy of each method and its correlation to relapse and survival of patients with stage II melanoma. In stage III patients, a similar workup of the most proximal nonsentinel node in the full lymph-node dissection specimen will indicate the accuracy of each methodology to detect nodal metastasis beyond the SN and the prognostic significance thereof. These findings will be correlated to the results of sequential blood testing by RT-PCR and by tumor marker assays for S100, TA90, and angiostatin. In addition, tumor-positive and tumor-negative SNs will be assessed for activated cytotoxic T lymphocytes and downregulation of dendritic cell functions.