Inter-individual and inter-ethnic differences in drug response have been regularly found in clinical practice. This is not surprising given the remarkable diversity in genetic polymorphisms, environmental factors, cultural contexts, and treatment settings. Although some of the key research reports and pertinent data have been summarized in previous chapters, systematically conducted studies in this field remain scarce, sporadic, and lacking in consistency (Lin et al., 1999). Ethnic and sociocultural variables are rarely analyzed or controlled in published studies on drug effects. Such paucity of cross-ethnic data exists even though there is widespread use of psychotropics to treat people with mental disorders globally. There are compelling reasons why research in this area is very much needed to understand cross-cultural differences in psychopharmacology better. There is significant demographic shift with increasing multicultural populations in both Western and non-Western societies. As a consequence, there has been a significant growth of cultural psychiatry internationally. For instance, Asians represent more than half of the global population, and all the major psychotropics are widely prescribed in Asia. With increasing pressure on the health dollar, there is a need to improve the cost-effectiveness of pharmacotherapeutic agents by reducing the morbidity and mortality of medication side effects occurring in drug-sensitive individuals and populations (e.g., in many parts of Asia). Given that factors involved in determining inter-ethnic differences in drug response are often similar to those responsible for inter-individual variations, advances in cross-ethnic psychopharmacology can contribute to greater understanding of individual differences as well (Lin et al., 1993).