Nitrofurantoin is used in the treatment of, and to prevent, urinary tract infections. Since this chemotherapeutic agent was introduced in the fifties, quite a number of cases of acute and chronic pulmonary damage have been reported that were conditioned by nitrofurantoin. This is a report on three cases of pulmonary nitrofurantoin reactions, one of them acute and two chronic. All three patients were examined with the inclusion of bronchoalveolar lavage and transbronchial lung biopsy. In all three cases alveolitides of varying activity were confirmed. The radiological and CT findings are described.