The etiology of heritable diseases may be elucidated by localizing genes conferring susceptibility and by subsequent biological characterization of these genes. To localize genetic components for multifactorial traits, both hypothesis-driven candidate gene and hypothesis-free genome scan approaches have been applied. To date, only a handful of results have been reproduced in either a different cohort or model organisms. The integration of genetic approaches with high-throughput genomic techniques is very promising. Unfortunately, most genetic studies completely ignore strong nongenetic effects such as low education and poverty even though these factors are well-known to predict, for example, obesity. Thus, what are most needed in future research are statistical methods for discovering sets of susceptibility genes and environmental factors, as well as systematic verifications of the gene–environment–disease network.