Recurrent optic neuritis and the subsequent development of multiple sclerosis in children, particularly in Asian countries, are not well known. We report on recurrent optic neuritis and subsequent multiple sclerosis in 22 Thai children who were younger than 15 years of age at the onset of optic neuritis, had no previous neurologic illness, and were monitored for 6–20 years. Improvement of vision was observed in 8, 10, and 2 patients after the first, second, and third week of onset, respectively. Two patients had recurrent optic neuritis and the other 2 patients subsequently developed clinical definite multiple sclerosis characterized by hemiparesis at 6 months and myelopathy at 2 years later in 1 patient and myelopathy and brainstem dysfunction in the other at 4 and 6 years later. The frequency of subsequent development of multiple sclerosis after optic neuritis may be similar to that reported from the United States and European countries.