In a case-control study to examine the risk factors for bronchial carcinoma, 194 histologically confirmed cases of lung cancer and twice the number of controls (194 hospital controls, 194 population controls) were covered. In addition, the histological material obtained from 139 patients was assessed by a reference pathologist. In 107 cases (77%) the data coincided with the findings by the hospital pathologists. In women, young patients and persons with better general job qualifications adenocarcinomas and other bronchial carcinomas were seen more often and small-cell carcinomas as well as squamous cell carcinomas were rarer. Smoking did not entail any significant difference in respect of bronchial carcinoma risk. There was a significant risk increase among persons occupationally exposed to polycyclic aromatic hydrocarbons, arsenic, chromium, nickel and radionuclides in respect of squamous cell and small-cell carcinomas but not of adenocarcinomas and other histological types of carcinoma.