Ten percent to 40% of adults have intermittent insomnia, and 15% have long-term sleep difficulties. This article provides a review of the classification, differential diagnosis, and treatment options available for insomnia. We performed a MEDLINE search using OVID and the key words "insomnia," "sleeplessness," "behavior modification," "herbs," "medicinal," and "pharmacologic therapy." Articles were selected based on their relevance to the topic. Evaluation of insomnia includes a careful sleep history, review of medical history, review of medication use (including over-the-counter and herbal medications), family history, and screening for depression, anxiety, and substance abuse. Treatment should be individualized based on the nature and severity of symptoms. Nonpharmacologic treatments are effective and have minimal side effects compared with drug therapies. Medications such as diphenhydramine, doxylamine, and trazodone can be used initially, but patients may not tolerate their side effects. Newer medications such as zolpidem and zaleplon have short half-lives and minimal side effects. Both are approved for short-term use in the insomniac.