Delayed hypersensitivity (DH) to seven common antigens was examined in 38 men with chronic dermatophyte infections and in 20 controls. A similar percentage of the infected and the control groups reacted to four antigens. In addition to showing a low frequency of DH to trichophytin, the infected group also showed a significant reduction in their reactions to intradermal mumps skin test antigen and to a Rhus oleoresin patch test. Two members (5%) of the infected group were anergic to all tests. Patients with chronic dermatophytosis appear to have a relatively specific defect in DH to trichophytin, but their cell-mediated responses to other antigens may also be somewhat decreased. The subjects studied did not appear to suffer excessive morbidity from infectious diseases, other than dermatophytosis.