To investigate the long-term effect of cigarette smoke on pulmonary structure and function, we exposed groups of guinea pigs to the smoke of 10 cigarettes each day, 5 days per week, for 1, 3, 6, and 12 months. We found that the guinea pigs developed progressive lung destruction (emphysema) and alterations in their pulmonary function tests similar to that seen in humans with cigarette smoke-induced chronic obstructive lung disease. This method of smoke-induced lung destruction should provide a good model for the study of the early changes of emphysema.