[The significance of environmental factors for the cancerogenesis in old age by the model of iatrogenic carcinogenesis (author's transl)].

According to the WHO (1964) about 80% of human malignant tumours are supposed to be the result of an exogenous effect. Beside the exposition also an inherited or acquired disposition (genetical defect or basic condition with increased regenerative hyperplasia) as well as the age may play a role in the promotion of cancerogenesis. The significance of the advanced age is expressed in the cumulative effect of different exogenous cancerogens with the scope of syncancerogenesis.