This study examined the influence of social support (perception and utilization) on diabetic control. Subjects were 178 patients with diabetes mellitus [insulin dependent diabetes mellitus (IDDM) = 26, non-insulin dependent diabetes mellitus (NIDDM)= 152]. HbA1c values was used as an indicator of diabetic control. Assessment of social support was performed using the Stress and Coping Inventory. HbA1c values were significantly related to the presence or absence of participation in a diabetic education program as well as scores on perception and utilization of social supports. The participation in the diabetic education program was not significantly associated with the two social supports, however, the two social support factors interacted significantly with one another. As for type of DM, these findings were stronger in IDDM patients. These results suggest that, in particular patients with NIDDM, although diabetes education is effective for decreasing HbA1c, a combination of the two social supports also decrease the HbA1c value, independent of diabetic education.