A retrospective study of 108 patients with myasthenia gravis who had solely ocular symptoms and signs at onset was carried out to identify factors influencing prognosis. Increasing duration of pure ocular myasthenia was associated with a decreasing risk of late generalized symptoms; only 9 (15%) of the observed generalizations occurred after more than 2 years of solely ocular symptoms. Increasing age at onset was associated with greater risk of respiratory crisis or death caused by myasthenia, whereas patients younger at onset had a greater chance of a benign outcome. Neither systemic curare tests nor responses to repetitive nerve stimulation had prognostic value.