The analysis of the molecular composition of serum immune complexes (IC) in autoimmune diseases has assumed growing importance in the evaluation of their clinical significance and possible pathogenetic role. Essential Mixed Cryoglobulinemia (EMC) is typically a disorder characterized by the presence of high levels of IC with pathogenic action, by reduced serum complement levels and by an antiglobulin activity of the cryoprecipitable IgM. In this report we refer on the preliminary results of a study on the molecular composition of the cryoprecipitable IC isolated from the serum of five patients with EMC. The methodology we adopted involves the solubilization at 37 degrees C of the washed cryoprecipitates and the purification of the IgG-containing IC by affinity chromatography through a Protein A-Sepharose CL4B column. The analysis of the molecular component was carried out by electrophoresis in polyacrylamide gel containing sodium-dodecyl-sulphate (SDS-PAGE) followed by Immun-Blot. Our results, although very preliminary, suggest that this kind of study appears really suitable for the detection of specific antibody or antigenic components in the IC molecules involved in the etiopathogenesis of essential mixed cryoglobulinemia.