A novel nitrilotriacetic acid adsorbent has been prepared for metal chelate affinity chromatography. The new resin is a quadridentate chelate former and specially suitable for metal ions with coordination numbers of six, since two valencies remain for the reversible binding of biopolymers. It has been found to chelate Cu2+ and Ni2+ strongly and to be superior to the known iminodiacetic acid adsorbent. Charged with Ni2+, it was evaluated for the ability to bind peptides and proteins containing neighbouring histidine residues. The remarkable specificity found makes it an attractive addition to the range of adsorbents for metal chelate affinity chromatography.