During the year 1979, 28 out of 95 patients with positive culture for acid-fast bacilli exhibited non-tuberculous mycobacteria (29.5%). In 15 cases the radiological and clinical findings were consistent with the diagnosis of tuberculosis, but only in one case (cutaneous lesion) was the pathology due to the mycobacteria isolated whereas in all others the bacteria was a saprophyte. This study suggests that non-tuberculous mycobacteria may be more frequent than expected in our region, and demonstrates the importance of their precise identification in order to stop their treatment. Nevertheless, in case of doubt and until identification results are obtained, such patients must be treated as probable tuberculosis cases.