This chapter reviews different approaches and their findings in pursuit of sleep genes, with a highlight on the complex nature of sleep genetics revealed by those approaches. The polygenic nature of sleep can be appreciated even in studies using single-gene approaches. A branch of forward genetics, quantitative trait locus (QTL) analysis is the choice for comprehensively elucidating the genetic landscape of complex phenotypes such as sleep. The systems genetics approach, on the other hand, identifies genes whose expression affects sleep-wake phenotypes, and thus the genes identified are likely components of the sleep regulatory machinery and not simply a response to changes in sleep-wake states. Using multiple genetic approaches over the last few decades, researchers have begun to elucidate the genetic basis of sleep, and in particular, have established multigenic nature of sleep.