Vertebrobasilar dolichoectasia is a relatively uncommon pathological entity and generally asymptomatic. We report a quite unusual case of unilateral motor trigeminal involvement with trismus, due to VD. Apart from tetanus or local morbid conditions of the mouth, trismus is often attributed to disturbed programming and co-ordination of the masticatory muscles within the mesencephalic nucleus. The possibility of truncal compression of the trigeminal motor root by vertebrobasilar dolichoectasia being responsible for masseter muscle spasm, in analogy with the pathogenetic mechanisms proposed in hemifacial spasm, is proposed as an alternative explanation in the present case.