The human population is heterogenous and consist of popolations of immense ethnic diversity.There are considerable allelic differences between human populations as well as individuals within each ethnic group as a result of molecular heterogeneity of the genome.This,in turn,is responsible for differential allelic expression of genes endowing then with polymorphic characters. The molecular diversity within genes is responsible amongst others, of disease resistance or susceptibility or for that matter drug response. Pharmacogenomics is the key to the understanding of diferential drug response in different patient in relation to genetic constitution. The relevation of such information at the molecular level would assist the pharmaceutical industry to address a therapy directed to each individual.The objective of this article is to understand the mances of the genetic repertoire and correlate it with disease gene identification,genes that have been or can be used as drug targets,identify candidate genes for drug development and recent trend in drug discovery