The records of 11,328 autopsies performed on patients who died of malignant disease between March 1944 and August 1974 were reviewed, and 816 cases (7.2%) demonstrated renal metastases. The most common primary tumors in decreasing order of frequency were lung, breast, skin (melanoma), and tumors of the genitourinary, gastrointestinal, and gynecologic tracts, respectively. Generally metastases were hematogenous, multiple, bilateral, less than 3 cm in diameter, and located throughout the renal parenchyma. Associated metastases were usually present in many other organs. Because methods to detect renal lesions depend upon their size, clinical recognition of renal metastases will be largely limited to that 10% which are greater than 3 cm in diameter.