In previous communications from this clinic it has been stated that the urinary alkaline tide is primarily due to the secretion of hydrochloric acid by the stomach, for the tide was absent in most cases of achlorhydria. This observation has been confirmed by Ackman and Davies. Further study showed that it was necessary to distinguish between alkalinity developing during the day-time and that shown immediately after awakening, for this latter change is frequently seen in patients where hydrochloric acid is not found in the stomach, and is probably due to the respiratory adjustment of the subject to waking conditions. Recently we have studied a patient with achlorhydria who showed a tide exactly resembling those found in normal subjects. It seems desirable for us to report this case because the absence of hydrochloric acid was found after histamine had been injected—a method giving as complete proof of functional disability of the stomach as can be obtained. In many cases where a urinary tide has been present, but hydrochloric acid apparently was absent from the gastric juice, further gastric studies have failed to confirm the abnormal finding of the first one, and it has been claimed by some that the presence of a satisfactory alkaline tide furnishes definite proof that the stomach secretes hydrochloric acid. The patient was a man 46 years old who was a mechanical engineer by profession. He had occasional periods of mild diarrhoea, and symptoms which were somewhat suggestive of the presence of a peptic ulcer. The stomach emptied rapidly, as frequently is the condition in cases of achlorhydria. Gastric analyses were carried out, and the reaction of successive samples of morning urine determined.