Forty-four Mycobacterium-spp. were isolated in 33 patients from an infectious diseases ward. All patients were HIV-positive and most of them were drug-abusers. M. avium-intracellulare was the most common type of MOTT (Mycobacteria other than tuberculosis) detected and the only microorganism isolated in patients with mycobacteriaemia. The radiometric method performed by the Bactec system enhanced the isolation rate of mycobacteria, especially from the bloodstream. The Gen-probe DNA hybridization system proved to be rapid diagnostic tool for the identification of strains.