Basic calculations for membrane receptor characterization, concentration and the affinity constant, are given including usual data linearization procedures. Determination of the specific radioactivity and maximum binding activity of the tracer and development of saturation curves from binding-inhibition experiments together with criteria for correction of non-specific binding, are presented both theoretically and practically in giving examples from the author's study of Luteinizing hormone (Lutropin) receptors in boar testis. The interest for physiologists of the receptor characterization is emphasized by underlying the regulatory aspect in hormone response of the variation of receptor concentration at the target cell surface in the case of spare receptors.