Pseudomonas aeruginosa was isolated from bronchoalveolar lavage fluid from 8 consecutive patients undergoing bronchoscopy at an infectious diseases unit. None of the patients developed signs of respiratory tract infection that could be ascribed to the organism. The source of contamination was the suction channels of 2 fiberoptic bronchoscopes which, due to a lapse in routine procedures, were not cleansed manually prior to disinfection with glutaraldehyde. Although rarely of pathogenetic importance, the possible presence of P. aeruginosa in lavage fluids should never be discounted, as it may indicate faulty disinfection of bronchoscopy equipment and thereby point to a risk of transmission of true respiratory pathogens such as mycobacteria.