The human N-acetylation polymorphism is a genetic trait phenotypically reflected by differences in N-acetyltransferase (NAT) activity with therapeutic agents (rapid and slow acetylation). Acetylation polymorphism arises from the allelic variations in human arylamine N-acetyltransferase 2 gene (NAT2), which results in the production of NAT2 proteins with variable enzyme activity or stability. Certain NAT2 traits may contribute to the occurrence of adverse drug effects and act as susceptibility factors for certain malignancies such as bladder or lung cancer. We report the results of NAT2 genotyping of ethnic communities in South India. One hundred and sixty-six unrelated individuals belonging to eight Dravidian ethnic communities of South India, with typical Dravidian features, were genotyped for their acetylation status. Slow acetylators were found to be predominant in these populations, with a frequency of 74%. The allele 6A was found in the highest frequency, while 5B/6A was the most frequent genotype. A novel deletion at 859 site was observed in one of these communities; this heterozygous deletion was linked to a homozygous mutation at 481 site. The predominance of slow acetylator genotypes in our study populations conforms to the results in most other Asian populations, where approximately 60% of the individuals have been genotyped as slow acetylators. Sex specificity for acetylator status in our study varied from population to population.