A group of amnesic patients with Korsakoff's disease were treated with a single 1 g dose of DL-threo-3,4-dihydroxyphenylserine (DOPS) and placebo (lactose) in a double-blind crossover study. Three hours following administration, patients were given a battery of psychometric tests to determine the effects of the treatment on memory functions. Administration of DOPS had a significant effect on performance on the Memory Passages test but not on any of the other measures of memory. The effect of DOPS on Memory Passages is similar to the response observed following administration of clonidine in Korsakoff patients. Blood pressure and pulse, measured before and every 2 h after treatment, were unaffected by DOPS.