A major breakthrough in the therapy of demyelinating disease has recently been disclosed by the Optic Neuritis Treatment Trial. Over the past 6 years the trial has accumulated evidence that a high dose of corticosteroids taken to treat patients with an isolated acute attack of optic neuritis reduces the rate at which multiple sclerosis develops over a 2-year period of follow-up. The findings of the trial have had an immediate impact on the neuro-ophthalmic and neurologic community in the USA; therefore, I have focused my review on this important topic.