Alcohol interacts with a suprising number of commonly used drugs: antibiotics, anticoagulants, antihistamines, digitalis, monoamine oxidase inhibitors, nitroglycerine, diuretics, heavy metals, insulin, iron, puromycin C, and many others. It also interacts specifically with sedatives, opiates, phenothiazines, antidepressants, and other psychoactive drugs. This review calls attention to these interactions and what we know of their mechanisms. The physician is cautioned about the use of alcohol by his patients taking other medications and about the frequent difficulty of ascertaining the extent of the patient's alcohol ingestion.