Delayed gastric emptying secondary to diabetic autonomic neuropathy (DAN) is a recognized risk factor for aspiration pneumonitis. The purpose of this study is to determine whether bedside autonomic function tests (AFTs) would predict gastric contents. Gastric volume and its pH were measured in 36 patients with diabetes mellitus (DM) and 15 nondiabetic patients at induction of general anesthesia for elective ambulatory surgery. Manifestations of autonomic dysfunction were assessed preoperatively in all 51 patients with five commonly used cardiovascular AFTs. According to the results of these five tests, 16 patients with DM met the criteria for the diagnosis and are called "DAN positive." The remaining 20 diabetics did not meet the criteria and are called "DAN negative." Fifteen patients without DM did not meet the criteria and are called "nondiabetics." Diabetic patients were significantly older and more obese than nondiabetics and those with DM more than 10 yr were more often DAN positive. Solid, undigested food particles were found more often in the gastric contents of DAN-positive patients compared to nondiabetics. Gastric liquid volume and pH were similar in diabetic patients (DAN positive and DAN negative) and nondiabetic controls. These results demonstrate that diagnosis of DAN by commonly used cardiovascular AFTs does not predict larger gastric liquid volume or lower pH, but does predict the presence of solid food particles.