Hypocalcemic crisis developed in a patient with acute alcoholic fatty liver. In addition to jaundice and marked hepatomegaly, the patient presented with hypocalcemic crisis associated with hypomagnesemia, low plasma 1,25(OH)2-vitamin D and undetectable plasma parathyroid hormone (PTH) concentration. Subsequent computerized tomographic scan and liver biopsy showed the presence of severe fatty liver. With the improvement of liver function, the serum calcium level increased, and was accompanied by normalization of plasma PTH, serum magnesium, and plasma 1,25(OH)2-vitamin D levels. Serial ethylenediaminetetraacetic acid infusion tests demonstrated the reversal of the impaired PTH secretion. Thus, hypocalcemic crisis in this patient appeared to result from transient hypoparathyroidism induced by magnesium deficiency.