Contractile motility of the gallbladder and plasma cholecystokinin (CCK) responses to egg yolk administration were studied in 28 diabetic patients and 12 normal subjects. The patients were divided into three groups: group A (n = 10) had no diabetic neuropathy, group B (n = 8) had diabetic neuropathy with little autonomic neuropathy, and group C (n = 10) had advanced diabetic autonomic neuropathy. In groups A and B, contraction of the gallbladder after egg yolk administration was not significantly different from that of normal subjects. However, in group C, gallbladder contraction was impaired (p less than 0.01-0.05), compared with that in normal subjects. After the administration of egg yolk, plasma CCK levels increased from 12.4 +/- 4.5 to 25.3 +/- 12.0 pg/ml in normal subjects. In group A, plasma CCK levels increased from 17.9 +/- 8.5 to 39.3 +/- 14.2 pg/ml, and in group B, from 15.2 +/- 5.1 to 38.3 +/- 9.9 pg/ml. In group C, however, plasma CCK levels increased from 33.1 +/- 13.9 to 72.4 +/- 31.9 pg/ml, and fasting CCK levels and responses to egg yolk were significantly higher than those in normal subjects and in groups A and B (p less than 0.01-0.05). In conclusion, this study showed that in a group of diabetic patients with autonomic neuropathy, gallbladder contraction was impaired despite the exaggerated CCK response to egg yolk.