An epidemiological study was performed in the county of Erfurt including all lung cancer patients of the years 1963, 1968, and 1972 to 1977, together 2,585 males and 358 females. The following results were found: 1. The incidence of lung cancer increased significantly from 1963 to 1977. 2. About 60% of all lung cancer patients were younger than 70 years. 3. In male patients squamous cell carcinomas prevailed with 44.8%. Small cell cancers came up to 34.6% and adenocarcinomas to 10.1%. Large cell cancers reached 10.5%. These types in female patients had a proportion to each other like 26.9%: 30.8%: 30.4%: 11.9%. The proportion of adenocarcinomas increased significantly during 1963 to 1977. 4. We found a non significant age relation of histological types. The adenocarcinoma and the small cell cancers dropped with rising age. 5. The classification of histological types and the conditions of detection of lung cancers did not change in the study interval. Therefore the altering of patterns of histological types, especially the increase of adenocarcinomas was attached to the beginning of cigarette smoking in younger ages and the increasing proportion of filter tipped brands as well to a variation of exposition against professional cancerogens. 6. Patients with adenocarcinomas have the highest survival rate after 5 years: 8.1%. Squamous cell lung cancer patients have a 5 year survival rate of 6.8%. Patients with small cell cancers and large cell cancers ranged at 2.7% or 2.6%. 7. Peripheral tumors of each histological type will be detected earlier by fluorographic screening than central carcinomas. Therefore the 5 year survival rates of peripheral cancers always are more favourable than that of central cancers. 8. For the problems in exact typing and staging we propose an internationally adjusted definition of tumor localization as a third parameter for prognosis.