A 50-year-old patient with Guillain-Barre syndrome developed a symmetrical, bilateral sixth nerve palsy which resulted in constant esotropia and diplopia. The patient was treated with both prisms and orthoptics, which eliminated the diplopia. This treatment also improved both fu-sional divergence amplitudes and vergence adaptation. Objective eye movement recordings revealed subtle abnormalities of fixation, pursuit and saccades, i.e., square-wave jerks and intermittent saccadic dysmetria.