To determine the epidemiology and clinical features of disease due to nontuberculous mycobacteria (NTM) in our institution, we reviewed the medical records of all patients from whom NTM isolates were recovered from 1988 to 1990 to extract selected clinical and laboratory data. On the basis of the likelihood of infection, patients were classified as having definite, probable, or unlikely NTM disease as defined by published guidelines. Of 80 patients who met the inclusion criteria, 17 had definite NTM disease, and 23 had probable NTM disease. No differences in age, sex, presence of underlying pulmonary or nonpulmonary disease, or chest radiographic abnormalities were noted between patients with and without NTM disease. More than 85% of all definite or probable cases were caused by Mycobacterium avium complex, Mycobacterium kansasii, and Mycobacterium fortuitum complex. The diagnosis of NTM disease was often delayed or missed, which resulted in unsatisfactory management of patients. There is a need to educate physicians about the diagnosis and management of NTM infections.