A comparison of Löwenstein - Jensen and penicillin blood agar media, which can be prepared in small laboratories, is made in routine diagnostic cultivations of Mycobacterium tuberculosis. Tuberculosis. Tubercle bacilli grown in Löwenstein - Jensen medium were inoculated in Löwenstein - Jensen and penicillin blood agar media in numbers of 100.000, 10.000, 1000 and 100 bacilli and their growth was detected in each medium. It was found that the growth in both media was the same Inoculations were made from 153 sputum specimens to each medium and 5 positive growth were obtained. 3 out of positive cultures were grown on both media, the other 2 positives were grown only on penicillin blood agar. None of the media showed contaminations. These findings suggest that the penicillin blood agar medium has at least the same, or even better qualities than the Löwenstein - Jensen medium.