The synthesis of a series of cholecystokinin analogues derived from the well-known antagonist Ge 410 (Suc-Tyr(SO3)-Met-Gly-Trp-Met-Asp-beta-phenethylamide) is reported. Replacements of L-Trp by D-Trp, Asp by Glu and Met by Nle were carried out and the resulting changes in biological activities investigated. All compounds synthesized were tested for their ability to inhibit CCK-induced contraction on isolated guinea pig ileum. SAR studies for these compounds are discussed.