Using affinity chromatography to eliminate TSH from normal human serum. Preliminary treatment to TSH with 33% saturated ammonium sulfate were coupled to agarose in alkaline condition and packed in column (1.2cm×40cm). Human normal sera were applied to the column at a flow rate of 0.25ml/min, and the column was washed with 0.01mol/L PBS(pH7.4) at a rate of 3ml/min. Materials adsorbed to the immobilized antibodies were eluted with 6mol/L guanidine-HCI. Between experiments, the column was stored in PBS-azide at 4℃.