The facilitated downstream processing of an intracellular, polyhistidine‐tagged protein, glutathione S‐transferase [GST‐(His)6], direct from unclarified E. coli homogenates using expanded beds of STREAMLINE chelating, has been investigated. A series of pilot experiments were used to develop preparative‐scale separations of GST‐(His)6, initially in packed and then in expanded beds. Packed beds of Ni2+‐loaded STREAMLINE chelating proved to have the highest 5% dynamic capacity for GST‐(His)6, of 357 U mL−1 (36 mg mL−1). When using immobilized Cu2+ or Zn2+, metal ion transfer was observed from the iminodiacetate ligands to the high‐affinity chelator, GST‐(His)6. The subsequent metal affinity precipitation of this homodimer resulted in operational problems. An equilibrium adsorption isotherm demonstrated the high affinity of GST‐(His)6 for immobilized Ni2+, with a qm of 695 U mL−1 (70 mg mL−1) and a Kd of 0.089 U mL−1 (0.0089 mg mL−1). Ni2+‐loaded STREAMLINE chelating was therefore selected to purify GST‐(His)6 from unclarified E. coli homogenate, resulting in an eluted yield of 80% and a 3.34‐fold purification. The high dynamic capacity in the expanded mode of 357 U mL−1 (36 mg mL−1) demonstrates that this specific interaction was not affected by the presence of E. coli cell debris. © 2000 John Wiley & Sons, Inc. Biotechnol Bioeng 67: 206–216, 2000.