We examined several kinds of immunocompromied patients for onyr,homycosis. The incidence of onychomycosis in the patients with connective tissue disease treated with corticosteroid was significantly higher than the incidences in the patients with solid tumors trcated with chemotherapeutic agents, in the patients with leukernia (WBC<1, 000/cm3), and in the control patients. Although conventional corticosteroid trcatment do not disseminate the superficial fungal infection, it may perpetuate the low grade dermatophytosis.