Dehydroepi-androsterone (DHEA) exhibits various behavioral effects in mammals, at least one of which is enhancement of memory that appears to be mediated by an interaction with the gamma-aminobutyric acidA (GABAA) receptor complex. We investigated the effects of a single oral dose of DHEA (500 mg) on sleep stages, sleep stage-specific electroencephalogram (EEG) power spectra, and concurrent hormone secretion in 10 healthy young men. DHEA administration induced a significant (P < 0.05) increase in rapid eye movement (REM) sleep, whereas all other sleep variables remained unchanged compared with the placebo condition. Spectral analysis of five selected EEG bands revealed significantly (P < 0.05) enhanced EEG activity in the sigma frequency range during REM sleep in the first 2-h sleep period after DHEA administration. In contrast, the EEG power spectra of non-REM sleep were not affected, nor were the nocturnal time course curves of plasma cortisol, growth hormone, or testosterone concentration. The results suggest that DHEA administration has a mixed GABAA-agonistic/antagonistic effect, exerted either directly or through DHEA-induced changes in steroid metabolism. Because REM sleep has been implicated in memory storage, its augmentation in the present study suggests the potential clinical usefulness of DHEA in age-related dementia.