Phenotyping of plasma plasminogen (PLG) was carried out by the method of agarose gel isoelectric focusing followed by immunofixation or immunoblotting. The allele frequencies calculated from healthy Japanese individuals (n = 795) were as follows: PLG*1 = 0.9440, PLG*2 = 0.0189, PLG*A = 0.0076, PLG*A2 = 0.0006, PLG*B = 0.0138, PLG*B2 = 0.0013, and PLG*C = 0.0138. The PLG phenotype distribution in a group of patients with cerebral infarction (n = 125) was also studied. The allele frequencies were PLG*1 = 0.960, PLG*2 = 0.016, PLG*A = 0.012, and PLG*B = 0.012. No statistically significant association was found between PLG types and cerebral infarction.