Achlorhydria that is due to antrum sparring atrophic gastritis is a characteristic finding in pernicious anemia. As a consequence of this achlorhydria serum gastrin level rise. Usually several signs are required for assessing a pernicious anemia: megaloblastic anemia, low serum cobalamin level, positivity of a Schilling test, low level of intrinsic factor in the gastric juice, existence of anti-intrinsic factor antibodies in plasma and/or in gastric juice. In this study the usefulness of the serum gastrin level is assessed. We report here the results in investigating sixteen patients with a pernicious anemia. All had: megaloblastic changes on bone marrow examination, serum cobalamin level lower than 150 pg/ml. For 14 patients the performed Schilling test was positive. For 2, no Schilling test was done, but anti-intrinsic factor antibodies were elevated. Serum gastrin levels were higher than 150 pg/ml (254 to 1770 pg/ml). In our patients with pernicious anemia, as a result of hypo or achlorhydria, serum gastrin increase was higher than in any other cause of hypochlorhydria: anti-acid treatment, vagotomy ... Measurement of serum gastrin is easy. High levels are simple to explain if found together with a sparing antrum atrophic gastritis and/or a low level of serum cobalamin. Serum gastrin measurement may be a cornerstone of rapid and reliable diagnosis of pernicious anemia.