A study of 336 patients with bronchogenic carcinoma was carried out in Chandigarh, Northern India. The findings suggest that its epidemiology differs in several respects from that in Western countries. Almost a third of all patients and 94*4% of the 54 women had never smoked. The peak frequency of bronchogenic carcinoma occurred between the ages of 51 and 60 years, 14-6% of the patients being aged less than 41 years. Of the 232 smokers and ex-smokers, 48-3% had smoked only cigarettes, 28*4% only bidis (made of naturally cured tobacco), 19-8% both cigarettes and bidis, and 3-4% hukkas. There was a clear association between duration of smoking and frequency of carcinoma. Tumours were classified in 287 (85%) of the patients. Squamous-cell carcinoma was relatively more frequent (32-4%) than any other tumour type and occurred almost exclusively in smokers. Adenocarcinoma was found in 13-2% of patients and was the most frequent tumour in non-smokers. No differences of histological type were found between cigarette smokers and bidi smokers.Bronchogenic carcinoma is being diagnosed in India with increasing frequency but it is uncertain whether this reflects a rise in its incidence or a greater availability of improved facilities for diagnosing it. Little is known about epidemiological aspects of the disease in India or whether it differs from Western countries in its age and sex distribution, the relative frequency of its histological types, and the contribution made by smoking to its aetiology.To obtain answers to these questions we carried out a study of patients with bronchogenic carcinoma who were seen at the Postgraduate Institute for Medical Education and Reseach at Chandigarh, the capital city of the States of Punjab and Haryana, about 250 km north of Delhi. A preliminary report on the findings in 150 patients, seen from 1973 to 1977, has been published elsewhere.' During the following two years a further 186 patients were seen; this paper reports our findings in the whole series of 336 patients, which we have compared with those reported in Westem countries. MethodsWe reviewed the case notes of every patient in whom a diagnosis of bronchogenic carcinoma had been recorded during the years 1973-9. The major-

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