Patients with achlorhydria and hypochlorhydria show a much greater disposition to gastric cancer. Further, the early detection of pernicious anemia presents a problem because of the plethora of proprietary hematinics. As an aid to cancer detection, the tubeless method of determining free hydrochloric acid in the stomach removes many of the previous inconveniences which have discouraged widespread use of this screening test. However, pyloric obstruction, impairment of small intestinal absorption, hepatic disease, and impairment of renal function may interfere with the accuracy of the test.