Recent dramatic advances in genetics, including the completion of the Human Genome Project in April 2003 and the more recent completion of the HapMap Project in Fall 2005, present an opportunity that we cannot, as practitioners in a field, afford to miss. Our disorders are not only familial but highly heritable. Identifying genes that either confer risk for psychiatric disorders or that are involved in treatment response could provide an inroad into the neurobiology of these disorders and/or mechanisms of treatment. Since the Human Genome Project was completed, almost all genes for Mendelian disorders have been identified. Our disorders, however, like many other large public health problems such as diabetes and heart disease, are "complex genetic disorders." The definition of complex disorder includes the lack of a clear Mendelian pattern of inheritance and the likely involvement of multiple genes, each having a small effect. Unfortunately, identification of these disorders is often plagued by the imprecise distinction between health and disease and a lack of direct correspondence between the genotype and the phenotype. The road to discovery, therefore, is likely to be fraught with some dangers and the strategies used to conduct genetic studies of psychiatric disorders should be carefully considered. Because genes do not code for hallucinations or anhedonia, genetics can only help us if we use its discoveries to further our understanding of the brain and behavior. Genetics can lead us to molecules or molecular cascades of relevance, but it remains the work of basic neuroscientists and basic behavioral scientists to cross levels of analysis to cells, neural systems, and the whole feeling, thinking, and behaving person. Nevertheless, genetics can direct us to study molecules and molecular cascades that we never suspected to be involved in psychiatric disorders (dysbindin and schizophrenia, for example) or shed light on molecular systems already implicated (catechol O-methyltransferase and cognitive deficits). Moreover, genetics may catalyze redefining of psychiatric nosology but only if clear links between genotypes and well-defined phenotypes and endophenotypes are established.