Lesions of the kidney present many pitfalls in diagnosis for clinical signs and symptoms are rarely pathognomonic. The interpretation of the initial symptoms is frequently misleading. Nausea, vomiting, malaise, indefinite abdominal pain, loss of weight or strength, nocturia, frequency of urination, hematuria, and fever are some of the presenting symptoms. Abdominal palpation, to locate masses or elicit tenderness, is notoriously confusing at times. We have noted a predominance of renal symptoms and signs in several extra-renal conditions. The cases presented represent mistakes in diagnosis, even after complete study. They illustrate only a few of the pitfalls for the unwary. Gastro-Intestinal Symptoms The gastro-intestinal symptoms, such as nausea and vomiting, are often late manifestations of renal disease that has given few, if any, symptoms referable to the genito-urinary tract. Conditions in the stomach, gall bladder, intestines, appendix, pelvis, and spleen may cause referred pain and symptoms that simulate renal disease. Nocturia and vomiting (1) have been reported in 40 per cent of a series of malignant disease of the kidney. The following case is illustrative of the predominance of gastro-intestinal symptoms in carcinoma of the kidney. Case 1. C. D., male, age 62 years. The patient complained of nausea, vomiting, and progressive weakness for the year preceding examination. Roentgen examination of the gastro-intestinal tract was negative. There was an indefinite, irregular homogeneous mass in the region of the right kidney. The pyelograms showed a constant deformity, with compression and irregularity of the pelvis, and loss of normal outline of the calices. Autopsy.—The gross specimen was a large tumor mass involving the right kidney. On section, little normal kidney tissue was found. The pelvic mucosa was free from any involvement. The renal vein was greatly dilated and invaded by the tumor mass. Microscopic examination showed areas of sclerosis, with obliteration of the major portion of the renal tissue. There were areas of proliferation and hemorrhagic changes typical of a primary carcinoma. The clinical manifestations in primary carcinoma of the kidney depend on the location, size, rate of growth of the tumor, and whether or not the pelvis is invaded. Metastasis usually occurs through the lymphatics. Dissemination through the blood stream is rare. There is a tendency to invade the surrounding structures, which makes operative removal difficult. Most cases show local recurrence. In advanced cases, the tumor may grow into the pelvis; if so, it is difficult to determine the primary site of the lesion. Pain Pain is probably the most frequent presenting symptom. Behan (2) estimates that 90 per cent of all disease begins with, or has, pain as a prominent symptom at some time during its course.