In June 2008 a 23-year-old immunocompetent came to our observation, without fever and with an occasional cough for 2 months, who showed two chest X-rays and a CT, performed respectively 60, 40 and 20 days earlier, that pointed to a small lobitis at the right lung base. The patient had already undergone several antibiotic therapies that had not changed the X-graphic framework. On presentation, routine blood tests and cultural examinations of sputum were carried out to detect common germs, fungi and TB bacteria (microscopic observation, cultivation and PCR), and a new antibiotic therapy (piperacillin/tazobactam) was started. Since the radiological picture appeared unchanged after 10 days of therapy and the examinations (microscopic observation and PCR) were negative, bronchoscopy with bacteriological evaluation of BAL was performed, which was positive to Mycobacterium tuberculosis, and then tubercular lobitis was diagnosed. Therefore a specific therapy - rifampin (RMP), isoniazid (INH), etambutol (EMB), pyrazinamid (PZA) - was started and changed after 10 days due to the growth of mycobacteria resistant to INH and EMB on examination of sputum. Consequently, the early use of PCR on BAL allows, in skilled hands, small aspecific lobitis to be diagnosed more rapidly than using cultural examination of sputum.