Due to recent reports claiming that gastrin is present in the gastric juice, the method for gastrin determination has been evaluated. Separate experiments showed that gastrin added to gastric juice disappears rapidly if the juice is not boiled or neutralized. A total of 82 patients with various abdominal disorders were examined. No or only a trace amount of gastrin was found in untreated, boiled, or boiled and neutralized gastric juice in every patient, including three patients with achlorhydria. Histamine injection (0.04 mg. per kilogram, subcutaneously) did not influence this and was without effect upon serum gastrin concentrations of nine duodenal ulcer patients. Because gastrin apparently is degraded rapidly by gastric juice, this study does not necessarily disprove that gastrin is secreted into the stomach. However, the virtual absence of gastrin in all specimens examined, including some collected directly upon boiling water bath during continuous gastric aspiration lends no support to this speculation. Because gastrin does not survive even a short exposure to gastric juice without degradation, we suggest that earlier reports on the presence of gastrin within the stomach are questionable.