Serum cholinesterase and N-acetyltransferase polymorphisms were investigated in unrelated individuals from different parts of South Korea. The frequency of the allele(Ac*S) controlling the slow acetylation was ca. 0.561; no atypical variants of normal serum cholinesterase which fail to hydrolyse suxamethonium could be found. The phenotype distribution of the two pharmacogenetic markers in different populations of the world is described.