The technique we have developed to couple lectins to agarose provides a very hydrophilic spacer arm between the protein and the matrix. This ensures maximum expression of the carbohydrate binding activity of the lectin. The linkage is very stable over a range of pH values and, unlike cyanogen bromide linkages, proteins are not leached off the gel by Tris or other routinely used buffers. In addition, residual charges generated during cyanogen bromide conjugation which can produce nonspecific binding are not present on the gel following our coupling procedure. Our agarose bound lectins are supplied at a constant concentration of lectin per ml of gel. The concentration at which each lectin is prepared is selected in order to achieve the highest glycoconjugate binding capacity per mg of lectin present in the gel. Before each lot is made available, its binding capacity is tested using glycoproteins or derivatives of glycoproteins known to bind to the particular lectin being evaluated. This provides a guideline for the user and assures the quality of our agarose bound lectins.