In order to study the relationship between plasma motilin and motility of gallbladder in patients with chronic renal failure (CRF). Gallbladder volumes were determined with ultrasound in 17 normal subjects and 22 patients with CRF. Fasting gallbladder volumes (FGVs) and postprandial residual gallbladder volumes in patients with CRF were much smaller than those of normal subjects (P < 0.01, P < 0.01). There was no significant difference of maximal percentage emptying of gallbladder between normal subjects and patients with CRF (P > 0.05). In 17 normal subjects oral erythromycin administration reduce FGVs and postprandial residual gallbladder volumes (P < 0.05, P < 0.05). In 22 patients with CRF oral erythromycin administration changed neither FGVs nor postprandial residual gallbladder volumes. Radioimmunoassay was employed to measure plasma motilin concentration. The results showed that mean level of plasma motilin of patients with CRF was much higher than that of normal subjects (P < 0.01). There was sighificant negative correlation between plasma motilin level and FGVs. It is suggested that hypermotilinemia may be one of the major reasons for motility disorder of gallbladder in patients with CRF.