A disease entity has been presented which is presumed to be caused by air pollution, but the exact etiology is still unknown. Early in its course this disease behaves much like acute bronchitis. Later it is almost impossible to differentiate from classic asthma. As the disease progresses over weeks or months, it becomes a form of asthmatic bronchitis. The patient receives little symptomatic relief from the usual treatment for asthma. The lack of response to nebuliza-tion with bronchodilators is documented by external spirometric studies. Patients with histories of asthma prior to coming to Japan who continue to have asthma in the Kanto Plain (Tokyo-Yokohama area) usually show good response to bronchodilators. The patients with this asthmatic bronchitis have more trouble in the winter months during periods of increased smog concentration. Coughing and wheezing are the most common complaints. Unremitting shortness of breath is experienced throughout the year. Severe attacks which are almost indistinguishable from status asthmaticus occur with upper respiratory infections. As the disease progresses (usually in the patient with symptoms who remains in this area for several years or who returns to the area after having had the disease during a previous tour), more shortness of breath is manifested. The patient by this time is usually receiving adrenal steroids and has been frequently hospitalized. It is at this time that all of the symptoms and signs of emphysema are present. This is more likely to occur in persons who are heavy cigarette smokers. Although the study is by no means complete, it is believed that there is evidence that air pollution, of unknown content, is the cause of much disability which, under certain conditions, may progress rapidly to emphysema.