Continuous 48-hour polygraphic recordings of sleep/waking patterns were performed on 14 patients with narcolepsy-cataplexy before and after 7-10 days of treatment of their nocturnal sleep with gamma-hydroxybutyrate (GBH). GBH improved the quality of night sleep by increasing the amount of slow wave sleep, reducing stage I, increasing sleep efficiency (percentage of time in bed spent asleep), and reducing the number of periods of short sleep under 15 minutes. Also nighttime REM sleep was reduced in latency and became less fragmented. The daytime period contained less slow wave sleep and REM sleep, and fewer episodes of prolonged sleep. Patients experienced reduction or loss of daytime attacks of irresistible sleep, cataplectic attacks, and other auxiliary symptoms. Residual daytime drowsiness subsequently improved on low doses of methylphenidate. Tolerance did not develop and there were no serious toxic side-effects. Four of the patients had been refractory to previous combinations of antidepressants and high doses of stimulants.