Previous studies on the effects of gamma-hydroxybutyrate (GHB) on the sleep and clinical response of patients with narcolepsy are reviewed. New information on 48 patients treated with GHB for as long as 9 years is presented. These studies indicate that 2.25 to 3.00 g of GHB, taken in conjunction with a low dose of a stimulant during the day, rapidly alleviate the symptoms of narcolepsy in most patients. Tolerance does not develop to this treatment regimen; neither have any patients discontinued the treatment because of side effects. In poor responders, daytime drowsiness and not cataplexy has been the most common residual symptom. Sleep studies reveal that GHB induces REM followed by slow wave sleep. Although total sleep time at night may be unchanged, sleep is less fragmented. GHB appears to be effective because it can induce the symptoms of narcolepsy and contain them at night. It is noteworthy, therefore, that the central biochemical changes induced by GHB also appear comparable to those found naturally in narcolepsy.