Many disorders of hypomagnesemia or renal origin are now recognized. Familial Hypomagnesemia, Hypercalciuria and Nephrocalcinosis is one of them. Few patients with this disorder were described in the literatures. The cases of two sisters from a consanguineous marriage with this syndrome are presented. Bilateral nephrocalcinosis in both of them was observed; interestingly one of them has a horse shoe kidney. The Glomerular Filtration Rate in both of them is decreased. The urinary calcium and magnesium were high in both of them where urinary excretion of uric acid and oxalate were normal. Serum magnesium was low in both of them (0.2-0.4 mmol/L) whereas serum calcium, phosphorus and potassium were normal. Serum Parathormone levels were abnormally high. Ophthalmological examination revealed that they have severe myopia with no other eye abnormalities.