Mycobacterium fortuitum and Mycobacterium cheloni are two species of the M.fortuitum complex presently considered to be pathogenic for humans. Out of 60 suspected cases of pulmonary tuberculosis with no previous antituberculous treatment, th re were 17 .strains (28.33%) of rapid growers acid fast bacilli, showed growth on - l'j;l i! -..a ; , Lowenstein-Jensen mediun within 7 days at 27°C. Using biochemical reactions .(catalnse, arylsulfatase, nitrate reduction, iron uptake, tellurite reduction) and growth on MacConkey agar without crystal violet, they were distingushed into 9 strains (52.94%) M.fortuitum, 5 syrains (29.41%) M.cheloni and 3 strains (17.64%) M.phlei.