We studied the effect of a low dose of neurotensin (2.5 pmol/kg/min) on meal- and cerulein-induced gallbladder contraction in 11 healthy volunteers by means of real-time ultrasonography. Ingestion of a meal caused a significant reduction in gallbladder volume which reached a maximum of 57 +/- 2% of the basal value at 60 min after the meal. The infusion of neurotensin caused a slight but not significant attenuation of the contractile response of the gallbladder to the meal (maximal reduction of 49 +/- 6%). Increasing doses of cerulein (10, 20 and 40 ng/kg/h, for 30 min at each dose) caused progressive reductions in gallbladder volume of 18 +/- 5, 72 +/- 5 and 89 +/- 4% with the three respective doses of cerulein used. The simultaneous administration of neurotensin did not significantly modify the gallbladder response to cerulein. The results indicate that neurotensin, at a dose of 2.5 pmol/kg/min, does not influence the gallbladder contraction stimulated by food or cerulein.