This work examined the effect of pressure (413-4410 kPa), temperature (333-393 K), solvent flow rate (10-25 mL/min), ethanol-to-water ratio (0-95%) and the feed loading (80-450 g) on hot pressurized fluids extraction of isoflavones and soyasaponins from defatted soybean flakes. A four-factor Taguchi experimental design was employed to optimize operational conditions of these extractions. Experimental results indicated that 95% of isoflavones and 76% soyasaponins were recovered from defatted soybean flakes by using hot pressurized 80% ethanol extraction at 383 K, 551 kPa and 25 mL/min with a 80 g feed loading. The recovered isoflavones were further purified by a solid-liquid column packed with Amberlite XAD 16-HP resin. The content of isoflavones in the collected fraction could be enhanced from 1 to 58% by weight. (C) 2007 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.