Psoriasis [OMIM*177900] is a common, chronic and papulosquamous inflammatory skin disease affecting approximately 2% of Caucasian. However, this disorder is rare among Japanese, Eskimos, West Africans and North American blacks and very uncommon in North American and South American natives. The causes for these variations are likely to be both genetic and environmental. Population-based studies and twin studies indicate that psoriasis is a heritable disease with a polygenic mode of inheritance with variable penetrance. Independent genome-wide scans have suggested the involvement of a large number of chromosomal regions (loci), and many candidate genes have been proposed. We discuss genetic approaches to the disease, results and interpretations of relevant studies, as well as future perspectives. Understanding the genetic basis of psoriasis will represent a major advance in our understanding of the disease and will reveal novel disease-specific biologic pathways.