This article presents experimental results on the influence of the electrode gap and electrode material on the Bingham characteristics of polymer-based electrorheological (ER) fluids. An experimental apparatus adaptable to various types of electrodes was established for this investigation. Three different electrode gaps and three different electrode materials were tested. For ER fluids, a water-based Arabic gum ER fluid and a dry-based polyurethane ER fluid were tested. The field-dependent yield stresses and current densities were demonstrated under various operating temperatures. In addition, time responses of the ER fluids were experimentally investigated for on-off states of an input electric field and at different operating temperatures. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 3636-3644, 2009