Electric stimulation of single anterior or posterior semicircular canal nerves induced disconjugate eye movements in monkey, cat, dog and rabbit. These movements were different but characteristic for each canal nerve stimulated in each species. This is in contrast to eye movements evoked by lateral canal nerve stimulation which were conjugate and horizontal in these species. We investigated the relationship of these disconjugate eye movements to acceleratory head rotations in the plane of the vertical canals. Ocular deviations were calculated which would oppose head rotations in several vertical planes. The axes for these rotations lay at 45°, 90° and 0° from the midsagittal plane of the head and were parallel to the plane of the lateral canals. These rotations corresponded to head movements which would have excited single anterior or posterior canals, bilateral anterior or posterior canals, or unilateral anterior and posterior canals respectively. The eye movements evoked by vertical semicircular canal nerve stimulation appeared to be the same as the eye movements which were predicted to oppose rotation in the planes of these semicircular canals. Eye movements from single anterior canal nerve stimulation which appeared disconjugate from the front of the animal were associated when viewed from the plane of rotation of the head. These data show that the degree of ocular dissociation and the direction of the eye movements can be mathematically approximated if the plane of the excited semicircular canal and the angle of the optic axis of the animal are known. The most important factor in determining the form of the induced eye movements from species to species is the lateral or frontal positioning of the eyes in the head. The results also show that the central neural organization which produces these movements must vary from species to species to provide the precise ocular compensation in direction which exists for acceleratory head rotation.