Clinical studies have shown that zolpidem, an original imidazopyridine derivative, induces and maintains sleep and does not have daytime side-effects. Polysomnography has revealed that this drug has several interesting qualities that benzodiazepines do not possess: stages 3-4 increase, stage 2 is unchanged or slightly reduced and no abnormal changes are detected on the EEG tracing. Like benzodiazepines, zolpidem slightly reduces REM sleep. The Multiple Sleep Latency Test confirmed that the drug does not cause daytime drowsiness. All the hypnotic drugs studied up to now worsen heavy snoring and obstructive sleep apnea syndrome. A controlled double blind cross-over trial assessed the effects of a single dose of zolpidem 20 mg on nocturnal breathing in patients with mild forms of sleep apnea syndrome. The results indicate that, at this dose, the drug does not overcome the existing contraindications to the use of hypnotics in this syndrome.