The aim of the present study was to investigate the effect of diet treatment on serum glucose, triglyceride (TG), total cholesterol (TC), high density lipoprotein-(HDL) cholesterol, low density lipoprotein-(LDL) cholesterol and very low density lipoprotein-(VLDL) cholesterol levels, systolic and diastolic blood pressure and electrocardiograms (ECGs) in patients with type 2 diabetes mellitus (DM). Twenty healthy subjects (mean age 45.9±3.7 years) and newly diagnosed patients with type 2 diabetes prior to receiving diet treatment (mean age 47.6±6.2 years) were included in this study. Diabetic patients were given a standard dietary treatment that was composed of 50% to 55% carbonhydrate and 30% fat (1200 kcal for women and 1600 kcal for men) for 2 months. No diet treatment was applied for control. For both groups serum glucose, TG, TC, HDL-cholesterol, LDL-cholesterol and VLDL-cholesterol levels, systolic and diastolic blood pressure and ECGs were measured at the beginning and end of the diet treatment. Although diet treatment decreased the elevated serum glucose in diabetic patients, it still remained higher than that in the controls. Diet treatment also decreased the elevated TG and VLDL-cholesterol in diabetic patients to control values. Although heart rate and systolic blood pressure were higher, diastolic blood pressure was not different in diabetic patients than those in controls. Ventricular hypertrophy was also observed in ECGs of 10% of diabetic patients. Diet treatment normalized all of these findings, except systolic blood pressure. This study showed that diet treatment could not normalize the high systolic blood pressure in type 2 DM. Thus, an effective way of controlling blood pressure should be taken to improve healing in DM.