Clinically important electrolyte disturbances such as hypokalemia and hypocalcemia have been well described in patients with hypomagnesemia of various causes. We undertook the present study to describe in detail the clinical characteristics as well as the acid base and electrolyte abnormalities in an effort to better understand the conditions that favor the appearance of this syndrome of hypomagnesemic hypokalemia and hypocalcemia, and the underlying pathogenetic mechanisms. A total of 35 adult patients (23 male, 12 female), aged 21-79 years, who exhibited profound hypomagnesemia, hypokalemia, and hypocalcemia on their admission were studied. The most common causes of the syndrome were alcoholism and cisplatin administration. All but 2 patients with diarrhea had inappropriate magnesiuria. Despite hypokalemia and hypocalcemia all patients exhibited renal potassium and calcium wasting. Eight alcoholic patients with alcohol withdrawal syndrome or acute intoxication had pure respiratory alkalosis, while 6 patients with severe hypokalemia presented with metabolic alkalosis. Three chronic alcoholic patients exhibited metabolic alkalosis coexisting with respiratory alkalosis, while 1 alcoholic patient had the syndrome of alcoholic ketoacidosis. Hyponatremia was evident in only 2 patients with clinical and laboratory evidence of extracellular volume depletion. Hypophosphatemia was observed in 12 patients mainly due to inappropriate phosphaturia. Finally, hyperphosphatemia was found in 2 alcoholic patients with severe respiratory alkalosis. In conclusion, patients with hypomagnesemic hypokalemia and hypocalcemia exhibit multiple interrelated acid base and electrolyte abnormalities and mainly hypokalemia due to inappropriate kaliuresis, hypophosphatemia or rarely hyperphosphatemia, respiratory and metabolic alkalosis, as well as mixed acid base disorders.