Sleep medicine is a relatively new field to which medical practitioners have a limited exposure. During the last 20 years, many categories of sleep disorders have been defined. Sleep disorders produce various, sometimes serious, symptoms that cause physical, neuropsychological, and psychiatric problems. Medical doctors should recognize what symptoms are related to sleep disorders and make a first step to establish treatment plans that can help the patients. Based on sleep pharmacology we can understand the mechanisms of sleep physiology and ultimately can make appropriate prescriptions for patients. In Korea, actually, the physicians usually prescribe hypnotics indiscriminately for sleep problems, without considering any various sleep disorders and precise diagnostic procedures. Insomnia is not a simple homogenous disease entity, thus the exact diagnosis is essential for appropriate treatment. Especially, primary insomnia has a psychophysiological origin. Hypnotic medication is just one of the several treatment modalities for insomnia. To certain patients, behavioral modifications, rather than hypnotics, are effective. In fact, antidepressants and benzodiazepines can aggravate certain sleep disorders. In this article, the author reviews nonpharmacological treatment of insomnia, the medication specific to different sleep disorders, and treatment guidelines of hypnotics.