Insomnia is problematic for many individuals, causing them to seek treatment. There is a long history of therapies aimed at restoring normal sleep patterns, each having its advantages and disadvantages. This review traces the history of insomnia drug therapies from chloral hydrate and the barbiturates through the benzodiazepines and explores the newest selective benzodiazepine receptor agonists, including zolpidem and zaleplon. The mechanisms of action of the benzodiazepine receptor agonists are compared and contrasted. A pharmacokinetic comparison is presented showing the importance that parameters such as dose, onset of action, lipophilicity, metabolites, half-life, and receptor-binding affinity have on clinical effects. The possible adverse effects of sleep aids are discussed, including residual sedation and psychomotor impairment, daytime anxiety, anterograde amnesia and cognitive impairment, rebound insomnia, and drug tolerance and dependence. Effects on sleep efficiency and staging are also discussed. Recommendations for the primary care physician on the selection of hypnotics are also provided. Benzodiazepine receptor agonists are often appropriate agents in the treatment of insomnia; however, individual drug and patient considerations are important in matching the most appropriate agent to the individual patient. Zolpidem and zaleplon, newer selective benzodiazepine receptor agonists, offer additional treatment options.