Abstract : 73 male patients with chronic bronchitis were studied between October 1962 and May 1964. A detailed smoking history was obtained on all patients and clinical, radiological and pulmonary function measurements made. Patients were classified as having either chronic asthmatic bronchitis or simple chronic bronchitis, and each disease was subdivided into 4 grades according to severity. A random sample of 83 male hospital in-patients who did not have chronic bronchitis but were of the same social class and age range as the patients with bronchitis were also studied. They acted as controls for the assessment of the role of smoking in the aetiology of chronic bronchitis. Significantly more patients in the chronic bronchitis group smoked than in the control group. Among smokers in both groups, the patients with bronchitis smoked more heavily, for a longer period and had a higher life-time tobacco consumption than the patients without bronchitis. The severity of chronic bronchitis was significantly correlated with both smoking intensity and life-time tobacco consumption. Patients with bronchitis who smoked cigarettes were compared with those patients who smoked "gouza", a type of tobacco smoking prevalent among Egyptian labourers and agricultural workers, and patients who smoked both cigarettes and "gouza". There was no difference in these groups of patients with chronic bronchitis in relation to duration of smoking before onset of disease, age at onset or accumulated tobacco consumption. J. R. T. Colley.