I present a proposal for a laboratory practice to generate and analyze data from a saturation equilibrium binding experiment addressed to advanced undergraduate students. [[superscript 3]H]Quinuclidinyl benzilate is a nonselective muscarinic ligand with very high affinity and very low nonspecific binding to brain membranes, which contain a high density of muscarinic receptors. These features allow the instructor to devote especial emphasis to evaluate ligand depletion, and therefore, stress the subtle but fundamental difference between total (added) ligand and free ligand concentration at equilibrium.