Four patients with combined immunocytopenia of unknown origin were investigated. Two patients with pancytopenia had allo- and autoantibodies against erythrocytes, granulocytes and thrombocytes. Two other patients with granulocytopenia and thrombocytopenia showed allo- and autoantibodies against granulocytes and thrombocytes. All patients went into a transient or persistent remission under immunosuppressive therapy. The normalization of peripheral blood correlated with the disappearance of antibodies suggesting that the cytopenia was caused by an antibody mediated autoimmune mechanism.