In spite of considerable efforts, no genes of major effect have been found across an entire diagnostic category in psychiatry. Possible reasons for this may include difficulties in defining the phenotype, the complex relationship between genotype and gene expression and population stratification. This last problem has often been managed by restricting genetic sampling to only one ethnic group. An unintended consequence of using this strategy is that the major repositories of genetic material for the study of psychiatric conditions in the United States suffer from a paucity of genetic samples from non-Caucasian groups. Thus, these groups are being relatively understudied in terms of the genetic antecedents to psychiatric disease. The authors provide solutions including the need to augment the representation of African-American, Latino and Asian-Americans among research participants; a more nuanced approach to identify ancestry; and the development of analytic and genetic strategies to handle the issue of ethnic heterogeneity in samples.