To investigate the clinical and radiographic features and the response to therapy of Mycobacterium kansasii infection in human immunodeficiency virus-infected patients, the clinical charts of 19 cases diagnosed during a 15-year period were reviewed retrospectively. Most patients were male intravenous drug abusers. Mycobacterium kansasii infection occurred late in the course of HIV disease and was associated with advanced immunosuppression. Thirteen patients had pulmonary disease, three extrapulmonary disease (2 with pulmonary involvement), and three pulmonary colonization. Most of them had fever and nonspecific respiratory symptoms; interstitial and alveolar infiltrates were the most common radiographic findings. Fourteen patients were given antituberculous treatment; among these, a clinical response was observed in 85%. Overall mortality was 63%, but only four patients died from active Mycobacterium kansasii disease. HIV infection has become the most important risk factor for Mycobacterium kansasii disease in our setting. Pulmonary infection is the most frequent form of disease and is usually responsive to antituberculous therapy.