The effectiveness and the safety of a new chemotherapeutic phenol derivative, clofoctol, was evaluated in adult hospitalized patients affected by infectious diseases of the bronchopulmonary tract. The clinical diagnosis included acute exacerbation of chronic bronchitis, acute bronchitis, bronchiectasis, pneumonia, bronchopneumonia and lung cavitary neoplasm. Expectoration, cough, dyspnoea, respiratory murmur and body temperature were considered as clinical factors to which an arbitrary score was given. Functional respiratory parameters including FVC, FEV1 and FEV1/FVC X 100 were also evaluated. All the patients were treated rectally with clofoctol 1500 mg daily for five days. Bacterial evidence of infection was obtained by sputum culture, which was repeated at the end of treatment. At that time, bacteriological results were 72.4% disappearance of baseline pathogens, 20.7% persistence of baseline pathogens and 6.9% presence of different organisms. Functional respiratory parameters were found to be significantly improved by treatment. Clinical results, arbitrarily evaluated on the basis of the overall assessment of laboratory and functional data, were excellent in 33.3%, good in 44.4%, fair in 5.6% and poor in 16.7% of patients. Tolerance was generally good; side-effects included maculopapular rash in 2 patients and rectal disturbances in 10 patients. In conclusion, for the treatment of bronchopulmonary diseases clofoctol offers an interesting alternative to antibiotic therapy.