Current treatment of hypercalciuria is still controversial, not being recommended calcium restriction since it may cause a negative balance with important consequences to bone metabolism. In adults, the use of biphosphonates (sodium alendronate) has shown a good response. Biphosphonates are synthetic analogs of the endogenous pirophosphate. Pirophosphate is the simplest form of phosphate. In 1968, Fleisch demonstrated that inorganic pirophosphate inhibits the precipitation of calcium phosphate. The differences between various biphosphonates are in the safety margin between their inhibitor effect for bone resorption and the inhibitor effect for mineralization; bone resorption inhibition has been their most widely spread application. The objective of this work is to analyze the clinical and biochemical effect of biphosphonates in patients with hypercalciuria, osteopenia and renal lithiasis.From 1996 to 2006 we treated 25 cases of recurrent renal lithiasis associated with hypercalciuria and primary or secondary bone mass loss. All cases were treated with sodium alendronate and oral calcium (1000-1200 mg/day). We analyze tolerance and treatment compliance, side effects, biochemical effects on blood and urine, effect on bone mineralization, and the outcome of lithiasic disease before and after treatment.All patients have followed the recommendations for the administration of the drug (sodium alendronate 10 mg/day or 70 mg/week), have had good tolerance without relevant side effects, and no one quit treatment. 76% of the cases have had remission of the lithogenesis activity and 24% reduction, and all cases have had an increase of bone mineralization.In this group of selected patients with recurrent lithiasis and osteopenia the treatment with biphosphonates alone or associated with thiazide diuretics has given good results in renal lithiasis control and bone demineralization. The extension of indications should be analyzed in a multicentric randomized study.