The value of orange juice consumption in kidney stone prevention was examined in 8 healthy men and 3 men with documented hypocitraturic nephrolithiasis. They underwent 3 phases of a metabolic study, a placebo phase and 2 treatment phases in which they ingested either 1.2 l. orange juice (containing 60 mEq. potassium and 190 mEq. citrate per day) with meals or potassium citrate tablets (60 mEq. per day) with water and meals. Compared to potassium citrate, orange juice delivered an equivalent alkali load and caused a similar increase in urinary pH (6.48 versus 6.75 from 5.71) and urinary citrate (952 versus 944 from 571 mg. per day). Therefore, orange juice, like potassium citrate, decreased urinary undissociated uric acid levels and increased the inhibitor activity (formation product) of brushite (calcium phosphate). However, orange juice increased urinary oxalate and did not alter calcium excretion, whereas potassium citrate decreased urinary calcium without altering urinary oxalate. Thus, orange juice lacked the ability of potassium citrate to decrease urinary saturation of calcium oxalate. Overall, orange juice should be beneficial in the control of calcareous and uric acid nephrolithiasis.