Abstract:An investigation was undertaken to test whether the dose‐response curve of a cholecystokinin‐like agent (ceruletide) could be established by administering it in graded doses sequentially on the same day. The results were compared to individual doses given on separate days. The gallbladder ejection fraction (EF) was calculated for each dose using the Tc‐99m‐IDA counts to represent the gallbladder bile volume. The mean ejection fraction following 1,2.5,5, and 10 ng/kg given sequentially on the same day was 10 ± 8,22 ± 12,53 ± 13, and 85 ± 3 per cent, respectively. The ejection fraction for 2.5,5, and 10 ng/kg given on separate days was 29.7, 57.14, and 93.3 per cent, respectively, and was similar to the values obtained when the identical dose was given sequentially on the same day (P<0.05). It is concluded that the sequential method is as accurate as the single‐dose regimen and carries the advantages of simplicity in the establishment of dose‐response curve for any future