In 1985, 17 genetic markers of three Korean. populations were studied for the polymorphisms affecting the genetic predisposition of individuals for possible atypical reactions against environmental agents and drugs as Hell as the characterization of the Korean groups using erythrocyte enzymes and serum polymorphisms. On this basis, inter-ethnic variability in the genetic polymorphisms has been examined. Ecogenetics and pharmacogenetics are concerned with the genetically determined consequences of exposure of a human population to environmental agents and drugs: 1) Alcohol and acetaldehyde metabolism have received considerable attention due to their health implications. In Orientals, acetaldehyde dehydrogenase isozyme seems to play an important role in the biological sensitivity to alcohol and possibly also in the pathogenesis of alcohol related organ damage. A comparison of the result of ALDH-1 isozyme deficiency obtained with those published by Goedde et al shows that the deficiency is less frequent (ca. 27%) in the Koreans than among other Orientals of Mongoloid origin (ranging from 35 to 57% in Vietnamese, Japanese, Indonesians, Chinese, Zhuang and Han). This provides a remarkable evidence of geographical differences of genetic markers among different ethnic groups of Orientals. However, Mongolians in Northern China also had about 30% deficiency. 2) N-acetyltransferase is responsible for the acetylation of isoniazid, sulfamethazine and many other drugs. Many populations are known to vary in the frequency of rapid and slow acetylators. The results of acetylator phenotype distribution was obtained by using the sulfadimidine test. The determination of Rapid and Slow phenotypes resulted in frequency values of 0.22-0.28 for the three Korean populations. For Chinese in 1984, a higher frequency of 0.47-0.58 for slow acetylation has been reported. 3) An association is known between a gene producing deficiency of serum α₁-antitrypsin (Pi) - expressing the relatively rare homozygous state of the ZZ type - and an early onset of lung emphysema as well as neonatal hepatitis. Pi subtyping of 440 Koreans demonstrated a total of seven different alleles. Only the M₁, M₂ and M₃ were observed in polymorphic frequencies and Mvar, I, S and G genes in the frequencies less than 0.01. In a study of 62 patients with liver cirrhosis, two other variants (P and Z) were observed at low frequencies of < 0.01. Comparing the few data available about Pi subtypes, the observed polymorphic gene frequencies in the present study are found to be similar to the corresponding values in Chinese populations as well as Mongolian, Korean and Zhuang minorities of Northern China. The combined frequency of M₁, M₂ and M₃ in our samples (0.988) is very close to 0.983 in Japanese and 0.994 in Eskimos. 4) Suxamethonium is a drug commonly used in anaesthetics as a short acting muscle relaxant during surgery. Suxamethonium sensitivity is occasionally manifested as prolonged apnea. Genetic variants of normal serum Cholinesterase which fail to hydrolyse this drug have occasionally been detected. As for some Oriental populations, also in the Koreans no atypical variant could be shown. 5) A polymorphism of δ-aminolevulinic acid dehydrogenase has been described. Thisenzyme is affected by lead, which causes a diminution in its activity. A possible correlation between lead exposure, ALADH activity and a phenotype of this polymorphism in industrial workers is under study. Geographic frequencies of ALADH seem to be uniform throughout Asia and Europe. The values are 0.89-0.90 in the Europeans and 0.94 in the Japanese; ALADH-1 is fixed to 100% in Africans. The following erythrocyte polymorphisms have been investigated: AcP, PGM and its subtypes, 6-PGD, EsD, GLO, and PGP. Only some interesting findings should be disscussed here: in the 6-PGD system, we found a new variant which we call 6-PGD Korea. We observed this variant in one individual of the island Cheju and in two from