Electrofocusing and agarose electrophoresis techniques both reveal polymorphism of ESD2, which may be subdivided into two different proteins, coded for by genes allelic to EDS* 1. After agarose electrophoresis, ESD2 is slightly more anodally located than ESD5, while the latter is considerably more acidic as revealed by electrofocusing in polyacrylamide gel slabs. Family studies have confirmed that each of the allele products behave as Mendelian characters; and the gene frequencies in a Norwegian population material are about 0.08 and 0.02 for the ESD*2 and ESD*5 alleles, respectively.