Gastric emptying time was measured by ultrasonography in 18 NIDDM patients with and without autonomic neuropathy, evaluated by cardiovascular autonomic tests and in 10 controls before and after a physiologic test meal. Six neuropathic subjects showed gastrointestinal symptoms such as fullness and early satiety. Blood glucose, gastrin and pancreatic polypeptide were evaluated before and up to 200 min after the test meal. The gastric emptying rate was similar in controls (275 +/- 45 min) and in diabetic patients without (260 +/- 49 min) and with autonomic neuropathy (257 +/- 48 min) (p = ns), while diabetic symptomatics showed a significant reduction of gastric emptying rate (420 +/- 19.7 min) (p less than 0.001). Basal serum glucose concentration was similar in all diabetic patients (132 +/- 18 mg/dl, 166 +/- 52 mg/dl, 161 +/- 61 mg/dl, p = ns). A basal value of serum gastrin was similar in all groups while the test meal produced a rise with a peak at 40' significantly higher only in symptomatics (195 +/- 58 pg/ml vs control 107 +/- 88 pg/ml, diabetics without and with autonomic neuropathy: 98 +/- 12 pg/ml and 88 +/- 22 pg/ml respectively; p less than 0.01). Basal and stimulated PP values were similar in all groups. In conclusion ultrasonography is a simple, reliable method to evaluate gastric emptying rate without any interference in the mechanism of digestion and absorption of nutrients. The presence of non specific symptoms, such as nausea and gastric fullness, may indicate an early gastric involvement as supported by sonographic evidence of impaired emptying.