Diabetes mellitus type 2 (DM2) is the most prevalent form of diabetes, and is caused by a combination of genetic and non-genetic factors. Genome-wide association studies have led to the identification of 20 genetic risk factors for DM2, for which the actual causal mutations are not yet known. Nevertheless, some of the genes connected with diabetes suggest that the pancreatic beta cell plays a central role in the development of the disease. In the meantime, detailed knowledge of the genetics of some specific forms of diabetes has already lead to changes in pharmacological therapy; patients could be put on sulfonylurea derivatives and no longer need insulin. This is the case, in particular, for 'maturity-onset diabetes of the young' (MODY) and for permanent neonatal diabetes mellitus (PNDM). It is not yet possible to predict whether genetic research into regular DM2 will lead to changes in therapy.