A qualitative and quantitative gustometric testing method using the filter paper disc on sweet, salty and sour tastes was evaluated in 30 patients with diabetes mellitus (type II, NIDDM) and in 30 healthy subjects (volunteers) in our hospital. The following results were obtained in this study. 1) The threshold of salty and sour tastes in diabetic patients obviously elevated in contrast to those in healthy subjects. 2) The total score which was calculated by the sum of each score about sweet, salty and sour tastes, significantly lowered in diabetic patients (diabetes vs healthy; 18.5±8.9 vs 27.4±9.6, p<0.01), especially so in the patients with complications with microangiopathies (diabetes vs healthy; 13.1±11.7 vs 27.4±9.6, p<0.01). 3) Patients who have been afflicted with diabetes for more than 10 years show the lower total scores of three tastes compared to those who have suffered the disease for less than 10 years (more than 10 years vs less than 10 years; 11.0±10.5 vs 20.6±7.2, p<0.01). 4) The total scores rose considerably in some of diabetic patients after the improvement of fasting blood glucose levels by diet alone (before vs after; 16.5±8.3 vs 23.0±6.6, p<0.01). It is concluded that the gustometric testing method using the filter paper disc may be useful in clinical evaluation of the taste impairment in patients with diabetes mellitus.