The diagnostic interest of a search for anti-intrinsic factor antibodies is emphasized from the authors research on more than 200 patients or controls. Antibodies of type I, so-called blocking antibodies, were detected in 66% of cases where the diagnosis of pernicious anemia was made. Type II, so-called precipitating antibodies, were found in 47% of patients with antibodies of type I and only in the latter. Certain etiological factors, already noted in the world literature, were found, in particular the link with the female sex and with blood group A. The specificity of these antibodies is very great and false positives are exceptional. We did not find them in any of the 104 controls. They were observed, however, in 5 of the 56 patients where the diagnosis of pernicious anemia was not definite, but it is likely that, in these 5 cases, pernicious anemia existed with some other disease. Our study also showed the limits of other methods of investigation of this disease; hypovitaminimia B12 is often corrected by treatment without proper inductions and B12 malabsorption on the Schilling test may not be corrected by the addition of intrinsic factor.