The prevalence of the atypical phenotype of pseudocholinesterase was looked for in 345 individuals living in Zaira district of Northern Nigeria by the differential inhibitory actions of dibucaine and sodium fluoride. The frequency of the atypical gene, E1a was found to be 0.9% and the frequency of the fluoride insensitive phenotype E1(f), was 0.74%. The atypical enzyme or the intermediate phenotype was not observed in any of the 42 patients with sickle-cell disease.
