Several immunologic abnormalities exist in patients with active sarcoidosis. Impairment of in vivo and in vitro cellular immunity is well known. Humoral immunity disorders are characterized by increase in polyclonal serum immunoglobulin, existence of circulating immune complexes and auto-antibodies. In the serum, these abnormalities are nearly the same than disorders observed during auto-immune diseases. We report 2 cases of patients where active sarcoidosis was associated with auto-immune disease. Then we discuss the relationship which could exist between the 2 types of diseases. The first patient was a woman (aged 66 years). She presented an active sarcoidosis and clinical symptoms of sclerodermia. The second patient, a man (aged 24 years), presented active sarcoidosis diagnosed 4 years ago. He had never received any treatment. Thrombopenic purpura occurred suddenly and needed steroid therapy. Antibodies to platelets were found in the serum. These associations raise some questions: 1) are they only fortuitous? such cases are rare but their frequency is perhaps underestimated; 2) could any common abnormalities of the immune response explain the emergence of the 2 diseases? 3) could one of the diseases favour emergence of the other? This hypothesis seems possible only if sarcoidosis is the initial disease. Eventually these associations also raise difficult therapeutic problems and must incite to explore precisely the immunity of patients with active sarcoidosis.