Because alcohol is so widely used as a social drug and benzodiazepines are so widely used as therapeutic agents, the number of persons who may be using both drugs concurrently is high. Despite this frequent concurrent use, interactions of major consequence are not common. Major interactions are pharmacodynamic, involving common actions of both drugs as sedatives. Excessive sedation from a combination of both drugs is a most important consideration when driving an automobile. However, it is well known that tolerance develops quickly to the sedative effects of benzodiazepines when used in anxiolytic doses. Also, one must balance the benefit from relief of anxiety versus possible impairment of function from oversedation. Abuse of benzodiazepines is almost exclusively among subjects who also abuse alcohol, doubtless due to the fact that the two drugs show cross-dependence. The clinical practice of avoiding use of benzodiazepines (or other sedative-hypnotics) in known alcoholics is sound and should avoid many potential problems.