Pancreatic and duodenal homeobox factor-1 (PDX-1) plays a crucial role in pancreas development, β-cell differentiation, and maintenance of mature β-cell function. PDX-1 expression is maintained in pancreatic precursor cells during pancreas development but becomes restricted to β-cells in mature pancreas. In mature β-cells, PDX-1 transactivates the insulin and other genes involved in glucose sensing and metabolism such as GLUT2 and glucokinase. MafA is a recently isolated β-cell-specific transcription factor which functions as a potent activator of insulin gene transcription. Furthermore, these transcription factors play an important role in induction of insulin-producing cells in various non-β-cells and thus could be therapeutic targets for diabetes. On the other hand, under diabetic conditions, expression and/or activities of PDX-1 and MafA in β-cells are reduced, which leads to suppression of insulin biosynthesis and secretion. It is likely that alteration of such transcription factors explains, at least in part, the molecular mechanism for β-cell glucose toxicity found in diabetes.