In this study, an electrorheological (ER) effect of the suspensions containing both native starch (S) and modified starch (MS) particles in corn oil (CO) under various externally applied electric field strengths (E) are reported. To prepare an ER active material, biodegradable starch was partially hydrolyzed and converted to its Li-salt. Both biopolymers (S and MS) were characterized by FT-IR, H-1 and C-13 NMR, SEM. energy dispersive spectroscopy (EDS), TGA and conductivity measurements. Suspensions of S and MS particles were prepared in CO at concentrations ranging from 5% to 40% by mass. Effects of various parameters such as sedimentation stability, particle size, dispersed particle concentration, electric field strength, shear rate, frequency and temperature onto ER activity of suspensions were investigated. Further, creep behaviors of S/CO and MS/CO suspensions were also investigated. (C) 2009 Elsevier Ltd. All rights reserved.