The intravenous dose response of a ceruletide diethylamine (ceruletide) was established by a simplified scintigraphic technique where multiple graded doses were given sequentially on a single occasion. The gallbladder volume was represented nongeometrically by 99mTc-IDA counts. The mean latent period, ejection period, and ejection rate were similar for all four groups of subjects given 1-20 ng/kg of ceruletide. The mean (+/- SD) ejection fractions after 1, 5, 10, and 15 ng/kg of ceruletide as the single dose were 19.4 +/- 11.9%, 59.6 +/- 26.0%, 55.2 +/- 23.3%, and 67.8 +/- 8.7%, respectively. These ejection fractions were similar to the values when the identical dose of ceruletide was administered sequentially either before or after another dose. A dose of 5 ng/kg produced the most physiologic type of emptying. Intravenous doses of 10 ng/kg and larger caused adverse reactions in 42% of the total doses in the form of abdominal pain, nausea, systolic and diastolic hypotension, or bradycardia. It is concluded that the dose response of a cholecystokininlike agent (ceruletide) can be established reliably by a scintigraphic technique where multiple graded doses are given on a single occasion.