The ability to digest lactose is a variable genetic trait in human populations. Two distinct phenotypes are present: lactase non-persistence (LNP) and lactase persistence (LP). LP trait is likely to have conferred a selective advantage in individuals who consume appreciable amounts of milk. In European derived populations a single nucleotide polymorphism (SNP) C/T-13910 residing 13.9 kb upstream from the lactase gene has been shown to define lactase activity, and several other SNPs in the same region have been identified in African and Middle East populations. We evaluated the frequency of C/T-13910 SNP among cattle domesticating groups of northern India. It was observed that frequency of LP phenotype and that of T-13910 allele of LP was much higher in these groups compared to those with no history of cattle domestication. This may be to due positive selection of LP associated genotypes with spread of cattle domestication in northern India. However, the introduction of T-13910 allele into India seems unclear and may require further research.