OBJECTIVES: I. Evaluate the ability of a slow-releasing formulation of neutral potassium phosphate to correct hypercalciuria and prevent recurrent stone formation in patients with absorptive hypercalciuria.

II. Evaluate the safety of this treatment. III. Compare the efficacy of potassium phosphate to that of potassium citrate.

PROTOCOL OUTLINE: This is a randomized, double-blind study. Patients are stratified by participating institution.

Patients receive potassium phosphate or potassium citrate tablets twice a day for 3 years.

PROTOCOL ENTRY CRITERIA:

--Disease Characteristics-- Absorptive hypercalciuria Intestinal hyperabsorption of calcium, i.e.: Exaggerated calciuric response to oral calcium load OR Fractional calcium-47 absorption greater than 0.61 Calciuria greater than 200 mg/day on random and calcium-restricted diet Normal or high fasting urinary calcium Normal serum calcium Normal serum parathyroid hormone No primary hyperparathyroidism At least 1 calcium oxalate stone within the past 3 years No struvite or carbonate apatite stones No noncalcareous stones No numerous stones making precise quantitation difficult No renal tubular acidosis --Prior/Concurrent Therapy-- No concurrent drug therapy for nephrolithiasis --Patient Characteristics-- Creatinine clearance at least 0.7 mL/min per kilogram No hyperkalemia No hyperphosphatemia No urinary tract infection Other: No predisposition to hyperkalemia, including concurrent use of the following drugs: Potassium-sparing diuretics Angiotensin-converting enzyme inhibitors Nonsteroidal anti-inflammatory drugs No active peptic ulcer disease No chronic diarrhea