Intermediate risk melanoma is defined by the following criteria: (1) a tumor thickness >= 1,5mm and (2) the absence of regional nodal macrometastases, as assessed either by clinical examination or, if sentinel lymph node biopsy (SLNB) or elective node dissection (ELND) are performed, by the absence of macroscopic evidence of disease. Patients with evidence of nodal micrometastasis by SLNB or ELND are eligible. The choice of performing sentinel node dissection will be left to the decision of each center, on condition to concern all consecutive patients and that all surgical procedures are completed before randomization of the patients . The centers have to inform their respective national study center if they perform SLNB or ELND and also if they change their surgical procedure.