The benzodiazepines are sedative hypnotic drugs, i.e., central nervous system depressant drugs, that may adversely affect the control of ventilation during sleep. Prescription of these drugs may worsen sleep-related breathing disorders, especially in patients with chronic obstructive pulmonary disease or cardiac failure. The most frequent users of sedative hypnotics are the polymorbid elderly with a secondary complaint of insomnia. Although the benzodiazepines may reduce sleep fragmentation, their long-term use may also cause health problems, such as complete obstructive sleep apnea in heavy snorers or short repetitive central sleep apnea in patients with recent myocardial infarction. Since drugs of this class vary in their effects, it is crucial to note the action of a given benzodiazepine on the control of vital functions during sleep.