The determination of octreotide acetate in compound formulations of Sandostatin and diamorphine hydrochloride by RP-LC is described. Octreotide acetate, diamorphine hydrochloride and their respective degradants, [des-Thr-ol8]-octreotide and 6-O-acetylmorphine, were baseline resolved using a Lichrospher-60 RP-select B column with a mobile phase composition of acetonitrile/phosphate buffer (pH 7.4, 20 mM) (35:65 v/v) with UV detection at 210 nm. The method is simple, selective, precise and suitable for the determination of octreotide acetate in admixture.