A flexible endoscope was used to obtain 223 tracheal washes from 191 horses in three clinical categories. Total cell counts, cytological and bacteriological examinations are reported and the features of the main cell types encountered described. The presence and degree of inflammatory airway disease was determined by a semiquantitative assessment of the neutrophil response and was an important consideration in the interpretation of the bacteriological results. Potential pathogens were isolated from approximately 30 per cent of samples. Cytological changes suggestive of lungworm infestation, virus infection and chronic airway disease are described. Haemosiderophages, indicative of pulmonary haemorrhage, were found in all horses in full training. The techniques used were rapid and simple and were found to improve the accuracy of diagnosis of pulmonary disease. Sequential samples were useful for monitoring the progress of clinical cases.