J-DOIT3 was designed to examine whether intensive therapy in which the targets of HbA1c (JDS 5.8%), blood pressure(BP) (120/75mmHg) and LDL cholesterol (80 mg/ dL) are extremely aggressive compared to the those adopted by the guidelines, would efficiently suppress diabetic macrovascular complications (DMC). Although previous studies failed to significantly decrease the risk of DMC by the intensive therapy for hyperglycemia presumably due to the marked increases in severe hypoglycemic events and body weight, the patients in the intensive therapy group in J-DOIT3 have shown well-controlled blood glucose as well as BP and LDL with a very few severe hypoglycemic episodes. Thus, J-DOIT3 is expected to provide the first evidence that tight glycemic control as well as BP and LDL can efficiently and safely suppress DMC.