The Authors, reviewing the Literature on asbestos-related Malignant Mesothelioma (MM), found that because of its very peculiar characteristics, the causal link between professional asbestos exposure and the development of this tumour is very difficult to define in respect to: diagnosis, causal link and individuation of possible culpable conducts. The evaluation of causal link in different medico-legal areas is studied by different criteria. In civil law the criterion of weak causality is followed to allow compensation for damages. For institutional purposes in INAIL, the definition of causal link is particularly facilitated by the legal presumption of origin. In fact it is sufficient, that asbestos-related lesions are ascertained in individuals who are or were exposed at any time of their professional life to the risk of inhaling asbestos fibres. In criminal law, the current approach of the Supreme Court is to demand evidence of strong causality, with a high logical probability and rational credibility, and beyond reasonable doubt, because criminal liability is personal as established in article 27 of the Italian Constitution. It is worth pointing out that all the levels of evidence indicated above must pass the test of scientific suitability or possibility.