Chronic tracheobronchial syndrome was diagnosed in eight dogs which had had a chronic mild cough for two to 13 months but were otherwise clinically normal. In five of them there was evidence of contact with other coughing dogs before the appearance of clinical signs and the majority at first responded favourably to antibacterial therapy. The coughing occurred mainly when the dogs pulled on their leads or became excited. Three cases had bronchoscopic evidence of active airway inflammation, and five had varying numbers of inflammatory cells (neutrophils) in bronchial aspirates. There was no evidence of excessive production of mucus in the airways of any of the dogs. Seven had an increased bronchial pattern on radiographs but only one of the dogs has developed chronic bronchitis.