We report a case of acute transient cold agglutinin disease, the etiology of which we could not determine with the available methods. Cold autoagglutinins had anti I specificity, high titers of the autoantibody (> 1:1,000) and the thermal range was relative wide. Our patient had severe haemolysis and immunosuppressive therapy with methylprednisolone and cyclophosphamide was administered. It is a question how much these immunosuppresive agents influenced the recovery, and in what extent it was a self limited disease with spontaneous recovery.