Gallbladder (GB) volume was monitored by real-time sonography in diabetics (n = 21) and healthy volunteers (n = 55) after a test meal. Seventeen controls and seven diabetics were obese; six patients had both autonomous and somatic neuropathy, and four had somatic neuropathy. Fasting GB volume was similar in controls and diabetics with and without autonomic neuropathy; it was correlated with body mass index (controls, r = 0.43, P less than 0.002; diabetics, r = 0.46, P less than 0.04), and was increased in obese subjects. Post-prandial GB emptying was decreased in diabetics. Those with autonomous neuropathy exhibited larger residual volumes than controls (P less than 0.03). Post-prandial GB emptying was slower and less complete in (non-diabetic) obese subjects and deteriorated further in diabetic obese subjects. GB fasting tone was normal, but GB kinetics were impaired in diabetics; obesity and autonomous neuropathy were correlated with GB hypomotility.