Mycobacterium kansasii was isolated from 25 patients with cancer who were cared for at the University of Texas M. D. Anderson Cancer Center (Houston) from January 1987 through December 1996. Two patients (8%) had disseminated disease, and 23 (92%) had pleuropulmonary isolates only. Signs and symptoms of mycobacterial infection at the time of diagnosis were often minimal or absent despite substantial radiographically evident involvement. The infections responded well to rifampin-based antimycobacterial regimens. M. kansasii is an infrequent but serious cause of pulmonary and, occasionally, disseminated disease in patients with cancer.