The acute effect of ethyl alcohol ingestion is to induce diuresis with excretion of free water and preservation of electrolytes. This occurs as the blood alcohol concentration is increasing and is due to the suppression by alcohol of the endogenous release of ADH. During a steady blood alcohol concentration, alcohol acts as an antidiuretic, causing retention of water and electrolytes. While at steady state, additional doses of alcohol will produce progressively smaller and eventually absent diuretic responses. The chronic effect of alcohol is to promote isosmotic retention of water and electrolytes due to increased ADH levels. Excess water and electrolytes are acutely excreted in response to additional alcohol ingestion. With the cessation of alcohol intake, this excess will be excreted over several days. Routine parenteral fluid administration to chronic and withdrawing alcoholics should be avoided. The role of potassium and magnesium in the genesis of specific manifestations of the alcohol withdrawal syndrome is not clear. Alcoholic patients may have electrolyte abnormalities due to alcohol-induced diseases, poor nutrition, or vomiting and diarrhea. Each case must be individually evaluated.