This chapter reviews the use of corticosteroids for acute relapses in pediatric multiple sclerosis (MS). Corticosteroids are used to treat inflammatory conditions as they modulate the immune system through multiple mechanisms. Corticosteroids are considered type A drugs for treating MS relapses in adults. In patients with optic neuritis (ON), high-dose intravenous methylprednisolone (IVMP) 1 g/day for 3 days has been shown to be effective at hastening recovery. Another study showed that patients receiving IVMP within 8 weeks of an acute relapse had lower mean Expanded Disability Scale Scores (EDSS) assessed at 1 and 4 weeks compared to placebo. Most adult studies suggest that high-dose IVMP should be dosed at 500-1000 mg daily for 3-5 days. Long-term use of corticosteroids is associated with numerous and substantial adverse effects. The side effects of prolonged exposure to corticosteroids include osteoporosis, neutropenia, weight gain, adrenal suppression, acne, increased skin fragility, hypertension, and psychosis.