Interferons are commonly used, frequently already as a standard drug, in a relatively wide spec- trum of indications in tumourous and non-tumourous diseases. The numerous undesirable thera- peutic effects include also relatively frequent induction of autoimmune processes which, however, only rarely is associated with marked clinical manifestations. The author presents an account on two patients from their own clinical practice treated with interferon alpha who developed complications which in the author’s opinion may be associated with autoimmunity (a patient with thrombocytopenia responding well to immunosuppressive treatment, originally treated on acount of renal carcinoma, and a female patient with pulmonary sarcoidosis treated for essential thrombocythemia). The authors present also a brief review of the literature on auto- immunuty induced by interferon.

        Key words: Interferon - Undesirable effects - Autoimmunity.