The effect of extrusion parameters, including adlay species (Taichung No. 1, Okayama zairai, Hatohikari, Hatomusume) and rice flour levels (0%, 25%, 50%) on the physicochemical properties (bulk density, radial expansion ratio, longitudinal expansion, water absorption index (WAI) and water solubility index (WSI)), and textural characteristic (hardness) of an adlay-based extrudate was investigated. The Hatohikari species had highest radial expansion ratio and longitudinal expansion, but lowest bulk density and hardness. However, the Taichung No. 1 species had lowest radial expansion ratio and longitudinal expansion, but highest bulk density and hardness. The Hatohikari species polished Adlay extrudates had the maximum WSI and minimum WAI However, the Hatomusume species had minimum WSI and maximum WAI The results also indicated that increasing the rice flour level resulted in an increase in extrudates' radial expansion ratio and WAI, however, a decrease in extrudates' longitudinal expansion, bulk density, hardness and WSI. (C) 2007 Elsevier Ltd. All rights reserved.