We examined the relationship of interdigestive gallbladder emptying with the different phases of the migrating motor complex (MMC) and with plasma levels of cholecystokinin (CCK) and motilin. In 10 volunteers 20 cycles of the MMC were recorded. In 11 cycles phase III occurred in antrum and duodenum (group 1). In nine cycles phase III was observed only in duodenum (group 2). In group 1 gallbladder emptying started at 30% of total cycle length and continued until the end of the cycle. Maximal gallbladder emptying was 33.3 +/- 3.3% (SE). In group 2 gallbladder emptying also started at 30% of total cycle length but ended at 60%. Maximal gallbladder emptying in this group was 24.3 +/- 3.1% (P < 0.05). Motilin levels were higher in group 1 than in group 2 during phase IIB (240.1 +/- 28.5 and 142.1 +/- 30.9 pg/ml, respectively, P < 0.05) and during phase III (210.8 +/- 24.3 and 93.5 +/- 12.5 pg/ml, respectively, P < 0.05). We conclude that: 1) phase III activities starting in the antrum are preceded by greater and prolonged gallbladder emptying, higher motilin levels, and higher intraduodenal bile acid concentrations than phase III activities starting in the duodenum and 2) no relationship between interdigestive gallbladder motility and CCK levels could be demonstrated.