One hundred cutaneous tumors were investigated immunohistopathologically for the expression of intermediate filament (IF) proteins. Epithelial tumors, such as basocellular and squamous cell carcinomas, cutaneous adnexal tumors, and metastatic carcinomas showed keratin positivity in a varying number of tumor cells with two keratin antibodies with different specificities. Neoplastic cells of fibrohistiocytic tumors, pigmented nevi, melanomas, hemangiomas, glomus tumors, and lymphomas were positive for vimentin, but not for keratin or desmin. Cutaneous leiomyomas and leiomyosarcomas, on the other hand, were positive for desmin. The results show that the typing of IFs enables the differential diagnosis between carcinomas and sarcomas or melanomas, epidermal appendage tumors, and mesenchymal tumors, and between fibrohistiocytic and leiomyocytic tumors, and therefore are of diagnostic value in histopathologic problems of the skin.