The University of Pennsylvania's Clinical Pharmacogenomic Epidemiology (CPE) initiative, an Exploratory Center (P20) for Interdisciplinary Research funded by the National Institutes of Health, seeks a more complete understanding of the genetic basis for variable responses to medications. We approach this through development of an interdisciplinary initiative among the fields of genetics, bioinformatics, pharmacology, epidemiology, biostatistics, and bioethics. The goal is to lower artificial barriers that divide biomedical researchers and impede scientific progress.