By using Chatanika radar measurements of the ionospheric electric field and conductivity, an attempt is made to estimate the extent to which the Cowling mechanism is taking place in the westward auroral electrojet. We assess the effectiveness of this mechanism in terms of the ratio &agr;=ISP /INH, where INH and ISP are the northward Hall and the southward Pedersen currents, respectively. Estimates of &agr; are made for regions in which the electric field had both westward and southward components in the midnight sector during high geomagnetic activity. It is found that &agr; varies considerably with latitude within the westward electrojet and that &agr; decreases with increasing INH. Assuming east-west uniformity of the associated ionospheric quantities, these variations indicate that significant portions of the charges carried by the northward Hall current (due to the westward electric field) are removed from the ''excess'' charge region without generating an intense polarization field. This implies that the classical Cowling mechanism is taking place only incompletely.