Genotype polymorphism studies at 15 highly polymorphic short tandem repeat (STR) loci were carried out in three genetically important minor caste groups (Yadav, Kurmi and Baniya) of Bihar, a eastern state of India to evaluate their significance in human identification and population genetics study. The selected communities practice endogamy. Despite of same geographical area, the physical features of Yadavs and Baniyas resemble North Indian Indo-Caucasoids whereas Kurmis resemble more to Indo-Austroloids. Among the chosen 15 loci, two are penta-nucleotide repeat: Penta-D and Penta-E, and 13 are tetra-nucleotide repeat: vWA D8S1179, TPOX, FGA, D5S818, D13S317, D7S820, D16S539, D3S1358, THO1, CSF1PO, D21S11, D18S51 and are validated for other population of India and world for forensic testing and human population study. Thirteen of these STR loci are present in the combined DNA index system (CODIS) [J. Forensic Sci. 44 (1999) 1277] and world-wide data is available.