A quantitative study of gallbladder emptying using 99mTc-HIDA as a bile tracer was performed with either CCK or a fatty meal as gallbladder stimulant. Its aims were to establish; (1) the reproducibility of CCK- and fatty-meal-induced gallbladder contraction, and (2) temporal patterns of gallbladder emptying following a physiological meal. Nineteen healthy, fasted volunteers were selected for 3-minute CCK administration (IV Boots Pancreozymin 2CHR units/kg) or a 40 g fatty meal. Each underwent repeat scans not less than 14 days after the first. Quantitative activity/time curves were drawn with computer analysis establishing gallbladder ejection fractions (GBEF) for each stimulus. Our results demonstrated: (1) poor reproducibility of CCK-induced gallbladder contraction precluding its diagnostic use, (2) improved but still variable meal-induced gallbladder contraction, and (3) evidence for a neurocephalic emptying response with a fatty meal stimulus.