(14C) 2-deoxyglucose (2-DG) autoradiography was used to examine functional activity in the pigeon accessory optic system (AOS) during visual, vestibular and combined visual-vestibular stimulation. Monocular horizontal whole-field visual stimulation resulted in preferential labelling of the contralateral nucleus of the basal optic root (nBOR), in medial and lateral, but not dorsal regions, as well as the contralateral nucleus lentiformis mesencephali pars magnocellularis (LMmc). Increased activation was also observed bilaterally in LMmc after vestibular stimulation alone. 2-DG accumulation was maximal during combined visual-vestibular stimulation in both nBOR and LMmc.