Among the numerous agents tested on melanoma, cytokines have attracted much attention over recent decades, in particular interferon-alpha (IFN-alpha). However, in a small number of experimental assays, homeopathic products have also been used. This study aimed to analyze the effects of INF-alpha and Lymphomyosot, administered individually or in combination, on the growth of B16F10 melanoma transplanted in C57BL/6J mice. Two experiments were performed using 72 young male mice, treated with 1 x 10(6) B16F10 cells and treated with phosphate-buffered saline (I), INF-alpha (II), Lymphomyosot (III), and both INF-alpha and Lymphomyosot (IV). Subsequent morphological and immunohistochemical studies were performed. All treatments produced a reduction in tumor weight with significant differences in those treated with INF-alpha and Lymphomyosot. INF-alpha reduced the cell proliferation index and the spread of inflammatory infiltrates and produced an increase in the extent of intratumoral necrosis. An antitumour effect was displayed by both agents, as was the cytotoxicity of INF-alpha and the immune response-stimulating effect of Lymphomyosot.