A retrospective study was carried out on six patients with contralateral inguinal lymph node metastasis from a melanoma of the lower extremity. All six patients were found to have had a previous homolateral groin dissection and in five patients there was intercurrent disease relapse in the leg before or at the same time as the appearance of contralateral node metastasis. Although the prognosis in these patients is unfavourable, two had a survival period of 24 and 32 months and two were still alive 27 months after contralateral groin dissection. In order to determine possible pathways of dissemination, lymphoscintigraphic studies of the leg were performed in another 16 melanoma patients who in the past had undergone a groin dissection. In 13 of them uptake in the contralateral inguinal lymph nodes was detected, indicating that groin dissection can lead to a different lymphatic flow pattern, which is often directed to the contralateral groin. Contralateral lymph node involvement may be an expression of regional disease. In such patients a contralateral groin dissection is advocated.