Between 1981 and 1990, cultures of specimens from 86 patients at State University of New York-Health Sciences Center at Brooklyn were positive for nontuberculous mycobacteria other than Mycobacterium avium/Mycobacterium intracellulare complex or Mycobacterium gordonae. The most common species isolated were Mycobacterium xenopi (33), Mycobacterium fortuitum (28), Mycobacterium kansasii (7), and Mycobacterium chelonae (6). Thirty-five patients (41%) had clinical and/or serological evidence of human immunodeficiency virus (HIV) infection. Patients from whom M. xenopi and M. kansasii were isolated were significantly more likely to be infected with HIV than were the remaining patients in this series. Most of the mycobacterial isolates were cultured from respiratory secretions. However, extrapulmonary infections with M. fortuitum, M. xenopi, M. kansasii, Mycobacterium terrae, and Mycobacterium scrofulaceum did occur among the HIV-infected patients.