To the Editor. — I started reading the article by Drs Lawhorne and Ringdahl 1 with interest. By the time I finished, I was angry and depressed enough to write this letter. Throughout the article, there was no mention of how vitamin B 12 deficiency can be scientifically assessed for clinical purposes. Current practice seems to emphasize the art of medicine, and also the economics of medicine under the guise of cost containment, at the expense of science. The workup of a patient with vitamin B 12 problems can be expensive and inconclusive, but it can also be objective and scientific with minimum cost. 2 One does not have to do Schilling or deoxyuridine suppression tests, measure vitamin B 12 levels, perform gastrointestinal series, etc, which are expensive and sometimes uninformative. There are simple tests that every physician orders routinely but perhaps does not look at critically. For example, the