Diabetes mellitus (DM) is a disease defined by biochemical hyperglycemia. Currently it is classified into four major categories: type 1 DM (T1DM), type 2 DM (T2DM), gestational DM (GDM) and other DM. Within each category, the etiology is still heterogeneous. The pathogenesis of most DM is multi-factorial, including many genetic and environmental factors. T1DM, T2DM and GDM are polygenic. In the category of other DM, there are at least six maturity onset diabetes of the young (MODY) and many other genetic syndromes associated with DM, which are monogenic in origin. In this review, we briefly summarized the current status of genetics in DM, described what has been done in this specific area in Taiwan and discuss what should be done after the era of genome-wide association study.