In 78 patients with hypomagnesemia in urolithiasis the clinical course of disease was established in relation to therapy and dynamics of changes of serum magnesium levels. Almost 70% of patients had multiple, bilateral or recurrent nephrolithiasis or nephrocalcinosis. 70% of patients had Ca-oxalate stones or bilateral nephrocalcinosis. In 52% of patients a long-term magnesium supplementation was necessary. Significant progress of nephrolithiasis and nephrocalcinosis was observed in 80% of patients with permanent hypomagnesemia and in 4% of patients with normalization of serum magnesium level. Three of 15 patients with hypomagnesemia and progress of disease were transplanted a kidney and two were treated by hemodialysis. All five patients with renal failure had bilateral nephrocalcinosis, in three of them familiar occurrence of nephrolithiasis and hypomagnesemia was found.