10.22376/ijpbs.2019.10.1.p1-12 Volume 1 Issue 3 2010 (July - September) The field of pharmacogenetics was stimulated in 1970s when Vesell and Colleagues demonstrated that plasma half-lives of many drugs are less divergent among monozygotic twin pairs than among dizygotic twin pairs. This paper reviews about various study methods of pharmacogentics such as unimodal , bimodal studies and trimodal studies.  Sachdev Yadav pharmacogenetics, unimodal study, bimodal study, trimodal study -