Forty patients suffering from Kaposi's sarcoma (31 males, a females aged from 18 to 80 years) were examined for the presence of mycotic invasion of the toe-webs, toe-nails and soles. Fungi were found without exception in all patients. In 35 patients all three sites were invaded; the remaining 5 showed no involvement of the toe-nails. The causative agent was T. rubrum in 31 patients. T. mentagrophytes in 7, E. floccosum in 2. Four subjects with T. rubrum infection also showed a super-imposed C. albicans infection in the toe-webs. The skin tests with Trichophytin and Candidin yielded a mildly positive response to the former antigen in 4 cases and to the latter in 8 cases. The strikingly high percentage of affected cases in this group of patients with Kaposi's sarcoma is discussed.