Effects of different initial eye positions on saccades evoked by electrical stimulation of the superior colliculus (SC) were investigated in alert monkeys with the head restrained. The dependence of saccade vector on initial eye position was studied quantitatively by multiple regression analysis. Following stimulation at 240 of 367 sites in the SC, saccade vector was influenced by initial eye position. The magnitude of eye position effects on horizontal saccade component was similar to that for vertical component. These effects were mostly found with stimulation in the caudal SC. Results suggest that eye position signals may control excitability of neurones in the SC.