relationship studies revealed that carbonylmethyl groups at both N-1 and N-5 positions and hydrophilic groups, such as the carboxyl group on the benzene ring attached to the ureido group at the C-3 position, brought about potent affinity and subtype selectivity for CCK-B/gastrin receptors. Several compounds showed excellent in vivo inhibition of gastric acid secretion induced by pentagastrin in anesthetized