Transtracheal punctures were performed in 193 miners of anthracosilicotic coal who presented with an acute exacerbation of chronic bronchitis. The transtracheal aspirates were bacteriologically positive in 104 patients. Branhamella catarrhalis was isolated in 15 patients; 10 of these responded to chemotherapy, as shown by the resolution of all symptoms and the disappearance of the organism on a repeat transtracheal puncture performed 48 hours after the end of treatment. One ampicillin-treated patient, whose bronchial secretions yielded a beta-lactamase-producing B catarrhalis, showed no improvement. But subsequent treatment with cefuroxime was followed by clinical and bacteriological recovery. B catarrhalis probably acted as an opportunistic respiratory pathogen in these patients, who were probably compromised hosts in view of their clinical history. B catarrhalis normally responds to the penicillins commonly used for respiratory infections, but if treatment fails a transtracheal puncture is essential to identify the strain and determine an appropriate antibiotic.