Conformation of the renin inhibitor peptide, Pro-His-Pro-Phe-His-Phe-Phe-Val-Tyr-Lys (RIP) has been studied in aqueous solution and in lipid bilayers using 500 MHz 1H NMR spectroscopy. Analysis of the NMR parameters indicates that in aqueous solution, RIP exists as a random coil. On incorporation into lipid bilayers, the peptide adopts a rigid and well defined conformation. The N-terminal end is stabilized by the hydrophobic environment of the lipid bilayer. The C-terminal end is located near the lipid-water interface and attains rigidity due to interaction with the phosphate groups of lipids. The observations emphasize the role of environment in stabilizing significantly different conformations of RIP in three different media--D2O, DMSO and lipid bilayers.