The Pi, Plasminogen and Paraoxonase systems are important ecogenetic markers, and the PGM₁ subtype is a population genetic marker which has been recently identified. 364 subjects, living in Seoul, Korea were examined. Pi and PGM₁ phenotyping was performed by polyacrylamide gel isoelectric focusing, Plasminogen phenotyping by immunofixation after isoelectric focusing, and Paraoxonase activity measurement by direct spectrophotometry. In Pi system, allele frequencies were estimated to be M₁=0.7665, M₂=0.1690, M₃=0.0577, P=0.0041, G=0.0014 and V=0.0014. In Plasminogen system, a functionally deficient allele, PLG B, was detected at a frequency of 0.0124 snd the frequencies of PLG 1=0.9835, PLG 2=0.0027 and PLG A=0.0014. The paraoxonase activity appeared to show monomodal distribution. For the PGM₁ subtype, the frequencies of the four major alleles were found to be as follows: PGM₁al=0.7060, PGM₁a2=0.1580, PGM₁a3= 0.0948 and PGM₁a4=0.0330. Two rare alleles, PGM₁6 and PGM₁8, were also detected and their frequencies were 0.0014 and 0.0069, respectively.