We reviewed 81 cases of secondary carcinoma of the kidney, the clinical detection of which still remains a challenge. All lymphomas were excluded from this study. There was no direct relationship of the cell type of the primary tumor to the degree of renal invasion. Generally, functional renal impairment was not a significant entity unless renal destruction was extreme. Ureteral obstruction was infrequent in this group. Angiography was helpful in determining the metastatic spread as well as the degree of renal involvement. The varied aspects of the primary tumor's pathophysiology have been a continuing challenge to early detection and successful therapy in any patient. Furthermore, the anatomic location and the peculiar biologic behavior of some primary tumors may make the clinical course and response to treatment unpredictable. Lungs, stomach, breast and contralateral kidney remain the common primary sources of malignancy likely to metastasize to the kidney, with an apparent period of occult growth and further metastases before symptoms appear, The possible delay in seeking medical attention, that is chemotherapy and radiation, as well as the aggressiveness of the primary tumor itself may contribute to the poor survival noted in this study despite the use of various therapeutic modalities.