Patients with community acquired pneumonia (CAP) previously treated with other oral antibiotics (Cephalosporins 35,3%, Macrolides 26,9%, Tetracyclines 14,1%, Quinolones 12,8%, other 10,9%) for at least 72 hours at home were considered for this national multicentre study. 43 hospitalized patients (17 males and 26 females) ranging between the ages of 19 and 79 were treated with Amoxicillin/Clavulanic acid (AMC) 1,2 g e.v., T.l.D. for at least 3 days. I.V. Treatments were switched to AMC p.o. after apyrexial status. Average treatment duration was 10,8 + 3.6. Sputum/B.A.L. samples were obtained from all patients submitted for microbiological exams in order to determine microbiological aetiology of CAP in patients who have failed on previous antibiotics. At the end of treatment, 30 patients (96,8%) were considered cured, while treatment failed in 1 patient (3,2%). 12 patients were considered not evaluable because serology was positive for M.pneumoniae (5 pts); for C.pneumoniae (3 pts.); 1 patients was positive for Mycobacterium tuberculosis; 1 patient was positive for HIV and Mycobacterium spp.; 2 patients were non-evaluable for lung or bronchial tumor. Not reported adverse events.