Work has been carried out on the development of an animal model for chronic bronchitis by exposing primates to cigarette smoke. An exposure system incorporating a mask and valve/timer system has been developed, and experiments with radio-active materials and measurements of blood carboxyhaemoglobin and nicotine levels have demonstrated that test animals inhaled smoke deep into the lungs. Monkeys smoked an average of 12 cigarettes a day, 5 days a week, for up to 6 months. During this exposure period the animals were put through a comprehensive range of pulmonary function tests, with regular measurements of lung mechanics, ventilation and blood gases. Changes in lung function, particularly pulmonary resistances, were observed in the test animals. The lung parenchyma of these animals at termination showed characteristic aggregations of alveolar macrophages with foamy cytoplasm which contained distinct brown/black pigmented granules.