Approximately 60 to 70 million adults in the United States alone are affected by insomnia. Daytime symptoms of insomnia include tiredness, lack of energy, difficulty concentrating, and irritability. Recent epidemiologic research focusing on quality of life has identified significant insomnia-related morbidities that relate to work productivity, health care utilization, and risk of depression. Insomnia is also associated with diminished work output, absenteeism, and greater rates of accidents. gamma-aminobutyric acid is the major inhibitory transmitter in the central nervous system and most currently prescribed sleep agents are benzodiazepine receptor agonists, which induce sleep by binding to the benzodiazepine receptor site of the gamma-aminobutyric acid -A receptor complex. In addition to sleep, benzodiazepine receptor agonists can cause a wide range of ancillary effects not directly related to sleep, including sedative, anxiolytic, muscle-relaxant, and amnesic effects, and have risks of tolerance, dependence, and abuse potential.