Studies to discover novel, potent and selective oxytocin antagonists are reported. Combinatorial libraries designed to End novel replacements of fragments of oxytocin antagonist L-371,257, identified pyrimidine, thiazole, indole and benzofuran as potential alternatives to the benzoic acid moiety of L-371,257. Additional investigations identified indole and benzofuran derivatives with potent oxytocin antagonist activity. (C) 2002 Elsevier Science Ltd. All rights reserved.