Publisher Summary This chapter presents the most common coupling procedures in bioaffinity chromatography (BAC). When selecting the method of attachment, the primary consideration to be kept in mind is the groups of an affinity ligand that can be used to form the linkage to a solid support without affecting its binding site. The attachment should not introduce nonspecifically sorbing groups into a specific sorbent. The linkage between the surface of the solid support and the affinant should be stable during adsorption, desorption, and regeneration. When bifunctional compounds are used for coupling, complications arising from the crosslinking of both the carrier and the proteins with one another can be expected and, therefore, suitable reaction conditions—such as pH, temperature, and time—should be maintained carefully during the coupling. The amount of protein to be coupled, the stability, and the biologic properties of immobilized biomolecules can be affected by the choice of the solid support and the method of coupling. When the attachment of the affinity ligand onto the solid support is terminated, it is necessary that the remaining active groups that are capable of coupling should be eliminated. Some of the complications encountered in the application of bioaffinity methods could be due to the neglect of deactivation.