Persons with advanced human immunodeficiency virus (HIV)-1 infection are susceptible to disseminated mycobacterial infections. In the United States, most such infections are caused by Mycobacterium avium or M. intracellulare (i.e., M. avium complex [MAC]). In less developed countries, M. tuberculosis is equally or more prevalent than MAC in persons with HIV-1 infection. Other mycobacterial species have been reported to cause disseminated infection in HIV-infected persons, including Simiae-Avium (SAV) group mycobacteria. SAV group organisms share characteristics of M. avium and M. simiae. Although disseminated (i.e., the isolation of a mycobacterial species from the blood) infection with M. simiae has been reported in HIV-infected persons, another distinct species within the SAV group, M. triplex, was characterized in 1996. Two cases of disseminated infection caused by M. triplex have been reported in HIV-1-positive persons. This report describes four HIV-infected patients from Bangkok, Thailand, and Lilongwe, Malawi, who were infected with SAV group organisms. Because different mycobacterial species are not susceptible uniformly to antimycobacterial agents, accurate identification of mycobacterial species causing an infection is crucial for directing appropriate therapy.