The characteristics of ligands immobilised into 1,1'-carbonyldiimidazole-treated cross-linked agarose have been further evaluated. Since the intermediate activated matrix (an imidazolyl carbamate-agarose) is susceptible to nucleophilic attack by free amino groups, but is relatively stable to oxygen nucleophiles, ligands ranging from simple organic primary amines, amino acids, proteins and other biological substances, which contain amino group functionality, can be bound to the agarose via a N-alkylcarbamate (urethane) linkage. This covalent linkage has been found to exhibit good chemical stability to mildly acidic and basic elution conditions. The use of 1,1'-carbonyldiimidazole-activated agarose in the biospecific affinity chromatography of immunoglobulins, present in normal and pathological sera, is described.