73 patients on artificial ventilation and presenting with localised or diffuse consolidation had broncho-alveolar lavage (LBA), in search for a causative organism, in a prospective fashion. LBA was done using a supple balloon catheter (LBA-c) which was placed blind down the intubation tube, until a distal bronchus was blocked (under radiographic control). The mean number of organisms found was 1.56 +/- 1.2. LBA-c alone provided a diagnosis in 31 cases (42%) and in association with blood cultures in 14 cases (19%). In 11 cases (15%) the consolidation was not caused by infection. In 14 cases (19%) the diagnosis was made by serology or blood cultures alone. Finally in 8 cases (11%) no diagnosis could be made. Thus LBA-c achieved an etiological diagnosis for the pneumonia in 45 cases (54.8%) and remained negative in non-infectious cases. The good tolerance of the technique as regards blood gases, its simplicity of operation (without a fibrescope) and its diagnostic reproducibility make LBA-c an option in the diagnosis of pneumonias on artificial ventilation.