Genetic variation at both the E1 and E2 loci of pseudocholinesterase was studied in 7 southern African populations. In the Ashkenazim and Afrikaners, E1 locus variation was observed and the frequency of the E1a or 'atypical' allele was found to be 0.017 in the Ashkenazim and 0.016 in the Afrikaans-speaking population, similar to those observed in other caucasoid populations. The E1s, or 'silent' allele, was found to occur in the Afrikaans-speaking population at a frequency 2-3 times greater than in other Caucasians, giving an increased risk of scoline-sensitivity. The rarity of the E1a in the Negro and Khoisan populations was confirmed. All 7 populations showed variation at the E2 locus with high frequencies of the E2+ allele in the Caucasians and San, while Negroes showed relatively low frequencies. Coloureds showed intermediate frequencies, consistent with their historical origins.