Two methods for detecting gastric achlorhydria, the conventional and the tubeless methods, were compared in a study of 114 hospital patients. Each patient had a disease that might be expected to interfere with the physiological mechanisms involved in the tubeless method. The fasting patients received 1.0 mg. of histamine phosphate subcutaneously to stimulate gastric secretion. After 45 minutes a urine specimen was obtained and a sample of gastric juice was removed for the conventional titration with dimethylaminoazobenzene (Töpfer's reagent) as indicator. The patient then received 2 Gm. of a cation exchange resin (containing 90 mg. of azure A) with 240 ml. of water. Two hours later a second urine specimen was obtained for comparison with the first. Appearance of the dye in the second urine specimen, indicating the presence of free acid in the stomach, was correlated with the amount of acid disclosed by titration. Discrepancies between the results of the tube and the tubeless methods were found in 12 patients, 7 of whom had renal disease. In 102 patients the results of the two tests agreed. The simplicity of the tubeless method recommends it for use as an office procedure and in screening large numbers of patients.