Recently a new cellulose acetate membrane for electrophoresis to analyze protein fractions, named SELECA-VSP, was developed by Toyo Roshi Kaisha Ltd. In advance of commercial supply, a study group was organized to investigate utility of this new membrane in comparison with SEPARAX-SP, a standard membrane for protein fraction assay widely used in Japan. As a member of this study group, our laboratory mainly investigated the difference between the two membranes when analyzing protein fractions in serum as well as ascites, pleural fluid, cerebrospinal fluid and urine. JOKO-CTE8000 was used as a protein fraction analyzer. When buffer lacking EDTA was used in electrophoresis of serum and ascites, the correlation efficiency between the two membranes in percentage of the β fraction was inferior to that of other fractions. When EDTA-containing buffer was used in analysis of serum and ascites, however, the correlation between the two membranes in β-fraction was improved to a comparable level to other fractions. The correlations between the two membranes were satisfactory in analysis of samples other than serum and ascites, regardless of the presence of EDTA in buffer. We conclude that this newly developed membrane has the similar performance to a standard membrane and could be applied in assay of protein fraction in clinical samples.