1. After intravenous administration of the non-nutritive sweetener, saccharin (10 mg/kg), to normal volunteers; the plasma concentration--time curve fitted a two-compartment open model with a terminal half-life of 70 min. Renal clearance was high and the dose was recovered quantitatively in the urine. The elimination rate and clearance were decreased significantly by concurrent probenecid administration. 2. After oral administration (2 g) more complex and variable plasma concentration--time curves were obtained and these were reflected in the urinary excretion of saccharin. The fraction absorbed was about 0.85 as determined by the recovery in urine and the area under the plasma concentration--time curves. 3. No indication of saturation of renal elimination was found after oral or intravenous doses that were many times the average daily intake.