Among 1648 patients diagnosed as diabetes in our diabetic clinic, Seoul National university Hospital for last l3 years (1957~1969). 56,4% had one or more complications. As the main complications, neuropathy was found in 331 (20,1%) of tatal patients, retinopathy in 89(5.4%) nephropathy Including.albuminuria in 204 (12.4%) and cardiovascular insufficioncy including hypertension in 389(23.6%), There were,321 (19.5%) diabetics complicated with infection, 180(10.9%) of whom were pulmonay tubrculosis. Ketoacidosis was found in 12 (0.7%) cataract in 47 (2.9%) and liver cirrhosis in 41(2.5%). Through more detailed observation on 826 diabetics with complications, we found that these complications had some relationship with patient's fasting blood sugar level. The duration of diabetes had more significant relationship with the complications; the complications were found in 52.4% of the patiensts suffering for less than 3 years, 77.4 % for 3 to 10years and 95.5% for over 10 years. It might be conclued that the duratian plays an important role in inducing complication to the diabetic patients.