Investigators have failed to show the usefulness of screening electrolyte-sodium, potassium, chloride and bicarbonate-blood urea nitrogen and glucose levels. In spite of this, we observed that that practice continues to be widely used at our university medical center. Using a form of consensus analysis, we examined the records of 301 admissions to the medicine service to determine whether laboratory tests were done for diagnostic or screening purposes and whether screening test results led to changes in patient management. Of the 1,764 tests done, 716 (40.6%) were for screening purposes. Only 2 (0.3%) screening test abnormalities led to any therapeutic changes, and many false-positive tests led to unnecessary diagnostic retesting.