Insomnia, a remarkably common disturbance in a basic biologic function, arises from multiple psychological, physiologic, and environmental factors. Transient insomnia usually resolves spontaneously. Short-term insomnia is usually normalized by coping with acute changes in a medical condition or a relationship. In patients with insomnia caused by stressful life events, a short (ie, 10 days or less) course of a short- or intermediate-acting benzodiazepine hypnotic may be indicated. Long-term insomnia deserves comprehensive evaluation. Psychiatric disorders are common in patients with long-term insomnia. In patients over age 50, intrinsic sleep disorders are more prevalent. Behavioral therapy, including improved sleep hygiene, stimulus-control techniques, and sleep-restriction therapy, is preferred in the management of long-term insomnia. Pharmacotherapy (eg, low-dose antidepressant or benzodiazepine) is best used as an adjunct.