We report the synthesis and the affinity data at both the peripheral (PBR) and the central benzodiazepine receptors of a series of N,N-dialkyl-2-phenylindol-3-ylglyoxylamide derivatives III, designed as conformationally constrained analogues of 2-phenylindole-3-acetamides II such as FGIN-1-27. Most of the new compounds showed a high specificity and affinity for PBR, with K(i) in the nanomolar to subnanomolar range. The most potent ligands (4-7, 9, 13-27) stimulated steroid biosynthesis in rat C6 glioma cells with a potency similar to or higher than that of classical ligands. The SARs of this new class of compounds are discussed.