Mycobacterium szulgai is a scotochromogenic species that has recently been recognized as a human pathogen. Twenty-four cases of disease caused by M. szulgai in humans have been reported in the English-language literature. The clinical features of these cases were reviewed, and three additional cases (two pulmonary, one extrapulmonary) were studied. Pulmonary disease indistinguishable from that caused by Mycobacterium tuberculosis was the commonest type of infection caused by M. szulgai (18 of 27 cases). Olecranon bursitis was reported in three cases, and disseminated infection was noted in three cases occurring in immunocompromised patients. M. szulgai is more susceptible to standard antimycobacterial agents than are other nontuberculous mycobacteria, notably the Mycobacterium avium complex. Clinical improvement and cure of pulmonary disease can be anticipated when treatment includes at least three drugs effective in in vitro susceptibility tests. Surgical excision appears unnecessary in pulmonary disease but may be indicated in olecranon bursitis.