One hundred alcoholics treated for ethanol withdrawal were assigned randomly according to a double-blind protocol to receive four intramuscular injections of 2 g of magnesium sulfate at 6-hr intervals or an equivalent amount of normal saline. All patients were treated for signs of withdrawal according to a standardized protocol using orally-administered chlordiazepoxide for sedation. Three observers rated each patient for signs of withdrawal. There was no statistically significant difference between magnesium sulfate and placebo groups on any of the variables measured. The groups required equivalent amounts of chlordiazepoxide for control of withdrawal. The authors concluded that the routine administration of magnesium sulfate is not indicated for the management of alcohol withdrawal unless accompanied by cardiac arrhythmias.