In the basal secretion and in the gastric juice after stimulation with 6 µg/kg Pentagastrin in 15 persons a linear reciprocal relationship (r=−0.84) between the concentration of H+ and urea was demonstrated. The urea concentration in the non parietal secretion was 32 mg%, which corresponded to the serum urea concentration of 29 mg%. The interception of the dose relationship line was at a H+ concentration of 148 mEq/L. From this data it is concluded that urea is not secreted in the parietal secretion, but is excreted in the non parietal secretion in the same concentration as in the extracellular fluid.