The aim of this review is to prevent the role of immune complexes (IC) in blood disorders. Fundamental to this role are the multiple interactions among IC and humoral and cellular receptors which give origin to several biologically active compounds and to profound metabolic, functional, and morphological changes in the involved cells. The end product of all these interactions may be both a phlogistic process and an alteration of blood cells. On this basis, clinical and experimental evidence is provided to demonstrate that IC may be produced as a consequence or a side effect of blood disorders (explaining some peculiar disturbances or proving to be of prognostic importance) or may even be the primary pathogenetic event.