A patient with a complete unilateral conjugate gaze paralysis caused by a small lesion affecting the region of the right abducens nucleus, documented by magnetic resonance imaging, is reported. Eye movements were quantitatively evaluated using electro-oculography. A gaze-evoked nystagmus to the contralateral side and impairment of smooth pursuit and vestibular ocular reflex in the contralateral hemifield of movements were found. The differential diagnosis of conjugate gaze paralysis and the additional ocular motor abnormalities are interpreted in light of clinical and experimental findings.