Prophylaxis of uric acid stones with alternate day doses of alkaline potassium salts. Uric acid stone formation ordinarily is prevented by increases in the urinary pH after meals. This postprandial alkaline tide is lost in patients who make such calculi. Single dose, alternate day administration of an alkaline potassium salt will increase urinary pH and simulate this normal physiological mechanism. An important part of the regimen is patient self-monitoring to verify that the urinary pH increases to greater than 6.8, 1 1/2 to 2 hours after the medication is taken. In contrast to multiple dose daily regimens, this mode of base administration is tolerated better and easier to follow. In 17 patients, 7 with the recurrent gravel/colic syndrome and 10 with prior stones, this regimen abolished calculus formation during an average followup of 2 1/2 years. However, further studies are needed before this regimen can be recommended as standard therapy for uric acid stone prophylaxis. 