Research into the identification and functional role of neuropeptides has taken a prominent place in the field of neurobiology within the past 15 years. The type of knowledge available concerning these compounds is, by necessity, limited by the experimental methods currently in use. In this manuscript, an overview is provided of several types of experimental procedures that have been used to study neuropeptide actions in the central nervous system (CNS) and details are presented of the specific application of these procedures as they have been used in the authors' laboratories to study the physiological role of the endogenous brain/gut tridecapeptide neurotensin. The methods were chosen to illustrate research strategies for examining various aspects of peptide neurobiology and include radioimmunoassay (peptide content), high-performance liquid chromatography (HPLC) (analysis of peptide and its fragments), protein phosphorylation (signal transduction), and behavior. Although by no means inclusive, it is the authors' hope that the reader may be able to apply these methods to their own research as well as gain an appreciation for the distance that yet remains on the journey into dissecting the function and physiology of CNS peptides.