The electrorheological characteristics of a fluid system with semiconducting poly(naphthalene quinone) (PNQR) particles, synthesized from a Friedel-Craft acylation, were investigated via a rotational rheometer equipped with a high voltage generator. The flow curves of these ER fluids under several applied electric field strengths and particle concentrations were constructed and their flow characteristics were examined via three different rheological constitutive equations of Bingham model, De Kee-Turcotte model and our proposed model. Our proposed equation was found to fit the data very accurately. (c) 2005 Elsevier Ltd. All rights reserved.