Instances of immune disorders which are apparently prodromic to the development of malignancy are described. These include one case of pulmonary granulomatous asbestosis ending in IgA myeloma, two cases of Sezary syndrome with lymphocytic lymphoma, one case of Dühring’s disease with lymphoma, and three cases of hepatobiliary diseases developing hepatoma and skin carcinomas. The pathophysiology is discussed in the light of the transition between the dysimmunity and the neoplasia. Postulates evolving from these observations are: (a) the existence of tissue or organ-oriented T-cell surveillors (histosophocytes), (b) obligatory antecedent dysimmunity in cancer, (c) therapy must be directed to the dysimmune situations rather than empirical augmentation of ‘cancer immunity’. All the transition syndromes presented four stages of immunologic evolution: (1) the initial stage of immune competence; (2) a stage of immune dysfunction, asymptomatic but when changes can be demonstrated; (3) a stage of overt, clinical, immunologic deficiency (prodromic, preneoplastic) when surveillance is inappropriate, and (4) a stage of clinical manifestations of the malignancy (immunodecadence) with persistence of the immunologic disorder (perineoplastic). Allogenic carcinogenesis and its potentiation by immunosuppression is recognized as a fourth category of carcinogenic agent next to chemicals, radiations and viruses.