Esophageal function was prospectively studied in 50 consecutive insulin-requiring diabetes mellitus patients. The patients were stratified in three groups: A) 18 without peripheral neuropathy (PN); B) 20 with PN but no autonomic neuropathy; C) 12 with PN and autonomic neuropathy. Twelve patients (four B, eight C) had gastrointestinal symptoms including six with dysphagia. Radionuclide esophageal emptying was abnormal in 55, 70, and 83% of patients in groups A, B, and C, respectively. Eleven of the 12 (92%) symptomatic and 23 of the 38 (60%) asymptomatic diabetes mellitus patients had abnormal emptying. Five of six patients with dysphagia had abnormal emptying. Esophageal manometry was also performed in 15 patients. Twelve patients had abnormal manometry. These included nutcracker esophagus in two, achalasia in one, and increased percentage of multipeaked and simultaneous contractions in nine. There were no significant correlations between radionuclide esophageal emptying, manometric changes and symptoms. Gastrointestinal symptoms were more common in the presence of autonomic neuropathy. Delayed esophageal emptying was more profound in the presence of PN, but abnormal esophageal emptying was present in patients with neuropathy as commonly as patients without. Furthermore, the presence of diabetic retinopathy, duration or control of diabetics, and fasting blood sugar did not influence the frequency of abnormal esophageal emptying. Our data indicate that esophageal dysfunction is common in male diabetics even in the absence of clinical PN and retinopathy, suggesting that diabetic gastroenteropathy can occur in the absence of significant diabetic complications. Commonly observed abnormal esophageal manometry in diabetics is not necessarily accompanied by significant functional disturbances or symptoms.