The concept that acid gastric juice plays an essential role in the genesis of peptic ulcer is supported by a great deal of clinical, pathologic and experimental evidence. A number of points, however, are not yet clear. Apparently incompatible with this thesis is the alleged occurrence of chronic ulcer with achlorhydria. In this paper we wish to consider the question as to whether or not peptic ulcer occurs in the complete absence of acid gastric juice. In 1926 one of us (W. L. P.) reviewed the literature on this subject, studied a group of cases and concluded that there was no conclusive evidence that chronic ulcer occurs in the complete absence of acid gastric juice.1 The evidence usually offered to prove that ulcer may occur in the presence of achlorhydria was found inadequate either in demonstrating achlorhydria or in establishing the presence of chronic benign ulcer, or, indeed, in