Zolpidem is one of the newer medications developed for the treatment of insomnia. It is an imidazopyridine agent that is an alternative to the typical sedative-hypnotic agents. Zolpidem use is gaining favor because of its efficacy and its side effect profile, which is milder and less problematic than that of the benzodiazepines and barbiturates used to treat insomnia. Still, side effects are not uncommon with zolpidem use. We report a series of cases in which the patients developed delirium, nightmares and hallucinations during treatment with zolpidem. We will review its pharmacology, discuss previous reports of central nervous system side effects, examine the impact of drug interactions with concurrent use of antidepressants, examine gender differences in susceptibility to side effects, and explore the significance of protein binding in producing side effects.