Abstract N-( n-Propyl)-N-(4-pyridinyl)-1H-indol-1-amine hydrochloride (HP 749, I), a non-receptor-dependent cholinomimetic agent with noradrenergic activity, is a potential agent for the treatment of Alzheimer's disease. Pharmacokinetic studies in animals and humans showed that I was well absorbed and metabolized primarily to the N-despropyl metabolite (P7480, II) after oral administration. To facilitate the kinetic studies, a sensitive and selective high-performance chromatographic assay was developed. I and II are extracted from plasma by a mixture of cyclohexane—ethyl acetate and chromatographed on an isocratic reversed-phase high-performance liquid chromatographic system employing an analytical phenyl column with acetonitrile—ammonium formate as mobile phase. The concentrations of these two compounds, quantitated by internal standardization, are monitored by ultraviolet detection. The method is linear in the plasma assay over a concentration range of 0.5–500 ng/ml for both compounds with a quantitation limit of 0.5 ng/ml. The precision and accuracy of the calibration curves and/or method are less than 10%. The recovery of I and II from plasma is 63–74 and 63–68%, respectively, over a concentration range of 0.5–500 ng/ml.