This chapter discusses the experimental approaches that have been used successfully for purification of neurotransmitter receptors and other receptors of interest in neuroscience and behavior and the types of problems that are typically encountered in such studies. Purification of receptors for neurotransmitters, neuromodulators, opiates, drugs, and other chemical agents that act in the central nervous system, as well as the periphery, have become an essential step in molecular characterization of such receptors and facilitates elucidation of the biochemical and physiological events that take place on interaction of these agents with their binding sites. Based on pharmacological data, it is now clear that many neurotransmitter receptors exist as multiple subtypes, as in the case of dopamine (D1, D2, D3, D4, and D5 thus far) and serotonin (of which there are at least seven subtypes, e.g., 5HT1A, 5HT1B, and 5HT2), which differ markedly in their affinity for various receptor agonists and antagonists.