Two strains of the newly proposed species "Mycobacterium genavense" have been isolated, using the radiometric system (Bactec, Becton Dickinson), from the blood of two HIV-infected patients. Disseminated infections due to the new organism closely resemble those of the Mycobacterium avium complex, with prevalently intestinal symptomatology. We report here on the cultural behavior of the isolates, which are enhanced at pH 6, are inhibited by NAP, do not require supplements, and grow best at 37 degrees C. We also report on the antibiotic susceptibility of the isolates.