It has been suggested that direction asymmetry of simple cells by moving stimuli is due to asymmetries in flanking response regions in the receptive field, and that the stronger response in the preferred direction is caused by synchronized On- and Off-responses. The hypothesis was tested by comparing the response of direction asymmetric cells to moving and static stimuli. The hypothesis had a weak but statistically significant predictive power. However, both for cells where the predicted preferred direction was correct and where it was wrong, there was clear suppression of the response in the nonpreferred movement direction, indicating that direction asymmetry is due to inhibitory processes rather than to synchronized On and Off-responses. It is suggested that the asymmetries in flanking regions of static receptive field plots are caused by the same inhibition which produces direction asymmetry, thus explaining why the static plots have some predictive power on direction asymmetry.