Zolpidem is a novel non-benzodiazepine related hypnotic, which possesses an imidazopyridine structure. This drug has preferential affinity for the 3H-diazepam binding site in the rat cerebellum, while it is only weakly active at inhibiting 3H-Ro 5-4864 binding to the rat kidney. The potency of zolpidem at displacing 3H-Ro 15-1788 binding to rat cerebral cortex membranes is enhanced in the presence of GABA. On the sleep pattern of the electrocorticogram in the curarised rat, zolpidem induces a physiological type of slow wave sleep with rapid onset of action. Zolpidem differs from classical benzodiazepine drugs, in possessing an atypical binding profile to 3H-benzodiazepine receptors, and because it does not affect the sleep patterns.