The effect of acute high- dose glucocorticoid therapy on memory function in patients with acute optic neuritis (n = 9) and multiple sclerosis (n = 21) was studied. All patients had reversible impairment of long- term memory functions, whereas measures of short- term memory, attentional functions, and alertness remained unaffected. The effect of acute- dose glucocorticoid therapy on memory function in patients with acute optic neuritis (n = 9) and multiple sclerosis (n = 21) was studied. All patients had reversible impairment of long- term memory functions, yet measures of short - term memory, attentional functions, and alertness remained unaffected.