Genetic epidemiology--i.e. studies of the interaction between genes and environment--has lead to the identification of monogenic disorders and more recently of genes involved in polygenic diseases by means of family (linkage) and populations (association) studies. The recent complete sequencing of the human genome combined with new methods such as gene expression analyses with microchip technology and proteome analyses including bioinformatics increases the possibility to find genes involved in various diseases and help to identify new targets for therapy and/or prevention.