This paper is based on a study of 123 acute perforations of the stomach and duodenum treated in the First Surgical Division of the New York Hospital (Cornell Division) since February, 1913. Several previous publications1of smaller numbers of cases, have been made. The work has been done by a number of operators, the bulk by myself. The views expressed in this paper are based on my total experience in addition to the material here reported. Acute perforations of the stomach and duodenum stand second in the operations for acute conditions of the abdomen. While the perfectly typical cases are very easy to recognize, there are a good many borderline conditions which give rise to confusion. On the other hand, to make a perfectly sure diagnosis may require a certain amount of time spent in observation, which greatly jeopardizes the patient's chances of recovery. Fortunately in my experience, with