Argentation chromatography with silver ion macroreticular exchange resin was applied to diterpene resin acids and methyl esters. Best results for diterpene acids were obtained with silver/saturated ion exchange resin and solvent systems such as ethyl ether/acetone or acetone. The technique was applied in the isolation of a major component, identified as 20-nor7,7, 9-abietatrien-18-oic acid, from a commercial disproportionated rosin. -- AATA