: The chromatography of the peptide on the cationHis-D-Trp-Ala-Trp-D-Phe-Lys-NH 2 exchange cellulose Whatman Express-Ion Exchanger C has been investigated. Scale-down studies both in batch and using Mini Columns demonstrated a binding capacity of ¿300 mg per dry g and a recovery following desorption of ¿96% . The separation was scaled-up 40-fold to a laboratory column, where 100% (w/w) of applied peptide bound at 200 cm h-1 to give an operating capacity of ¿90 mg per dry g. Following desorption, recovery was ¿98% with some further puriücation of the peptide.