Renal tumors including renal cortical adenoma, renal cell carcinoma (hypernephroma), oncocytoma, angiomyolipoma (hamartoma), medullary fibroma, juxtaglomerular cell tumor, nephroblastoma (Wilms' tumor), mesoblastic nephroma, renal blastema, sarcoma, and secondary metastatic lesions are discussed. The syndromes of tuberous sclerosis, von Hippel-Lindau disease, and acquired renal cystic disease are reviewed. Renal cell carcinoma accounts for 85% of clinically relevant renal tumors. Development of renal cell carcinoma appears to be associated with loss of tumor suppressor genes on the short arm of chromosome 3. Over the past year, there were no major advances in the imaging of renal tumors. Ultrasound and computed tomography remain the standards, whereas magnetic resonance imaging, although having a high sensitivity for detection of renal masses, is used primarily for staging the inferior vena cava. The only effective therapy for localized renal cell carcinoma remains surgical resection. There are objective responses seen with immune modulation therapy (interferon-alpha, interleukin-2), but cures are infrequent.