The bioavailability of potassium and magnesium, and the citraturic response were determined for the new compound, potassium-magnesium citrate, in 14 normal volunteers. Results were compared to those of potassium citrate and magnesium citrate. Each subject participated in 4 phases of study: potassium-magnesium citrate, potassium citrate, magnesium citrate and potassium chloride. After stabilization on a metabolic diet, each subject ingested a single load of a test medication followed by timed urine collections for the next 24 hours. Test loads included potassium-magnesium citrate (49mEq. potassium, 24.5mEq. magnesium and 73.5mEq. citrate), potassium citrate (50mEq.), potassium chloride (50mEq.) and magnesium citrate (25mEq.). Urinary potassium, magnesium and citrate were measured for each collection period.Potassium-magnesium citrate provided an equivalent potassium bioavailability as potassium citrate and potassium chloride, and a comparable magnesium bioavailability as magnesium citrate. However, it gave the highest citraturic response, since the cumulative increment in urinary citrate post-load was 129mg. daily for potassium-magnesium citrate, 105mg. daily for potassium citrate and 35mg. daily for magnesium citrate. Thus, potassium-magnesium citrate gave an optimum citraturic response in addition to providing absorbable potassium and magnesium.