Abstract In this work the effects of electrode morphology on the slit flow of an electrorheological (ER) fluid via laser Doppler anemometry (LDA) are studied. For this purpose, oblique and corrugated electrodes were used. Under a.c.-conditions the ER-effect with the oblique and corrugated electrodes is greater in comparison to the case of smooth electrodes at the same voltage and pressure drop. An average factor of 2.0 and 2.5 (in the range 1–5 kV) describes the increase in the ER-effect for the oblique and corrugated electrodes, respectively. This increase in ER-effect is accompanied by a decrease in electric current. Under d.c.-conditions the ER-effect with the oblique and corrugated electrodes is somewhat better than with the smooth electrodes but only at a very low field strength. Increasing the field strength leads to a decreased ER-effect (in comparison to the smooth electrodes). This decrease of the ER-effect is always accompanied by a decrease in electric current (d.c.-field).