A single blind placebo controlled, cross-over study comparing a new microencapsulated potassium chloride tablet (MET) with two reference formulations of oral potassium, potassium chloride solution (PS) and potassium chloride wax-matrix tablets (WMT), was performed in 12 normal healthy volunteers. Urinary potassium excretion was the main criterion of comparison. Results showed that all three formulations have excellent bioavailability. This indicates that potassium absorption in the stomach is similar to that in more distant portions of the gut. The slow-release characteristics of both MET and WMT were confirmed. Clinical and pharmacological tolerance was excellent and no side-effects were reported with any of the potassium formulations studied.