A wide project of correlated and integrated experiments, performed for testing the carcinogenic potentialities of vinyl chloride (VC) (a monomer of high industrial importance), is presented. The results showed that VC induces Zymbal's gland carcinomas, nephroblastomas, and hepatic and extra-hepatic angiosarcomas, in rats, and pulmonary tumours, mammary carcinomas and liver angiosarcomas, in mice. The experimental data have oriented the clinical observations and the epidemiological investigations, which have recently led to the detection of the early cases of liver angiosarcomas among exposed workers in the U.S.A. and in the U.K. The experimental carcinogenicity bio-assays of VC should be considered therefore highly predictive. They represent a convincing example for developing experimental testing for all new industrial compounds, and for the ones already widespread, but of whose biological effects we are still ignorant.