Glucotoxicity, lipotoxicity and glucolipotoxieity are secondary phenomena following the primary pathogenesis, including the effects of genetic and environmental factors of type 2 diabetes. However, there exist two theories: (1) Lipotoxicity, presents before blood glucose rising, may trigger off a chain reaction which results in hyperglycemia. Hence the term " diabetes mellipidus" was proposed. (2) Hyperglycemia is a prerequisite for lipotoxicity. It seems more appropriate to state that (1) the glucotoxieity and iipotoxicity may present separately or concurrently in type 2 diabetes; (2) The combined glucolipotoxicity should describe the deleterious actions by higher levels of both glucose and free fatty acids on β-cell function, which finally causes progressive deterioration of insulin secretion.