In 1999 it was estimated that renal cell carcinoma (RCC) would account for 29,990 new cancer cases diagnosed in the United States (61% in men and 39% in women), and lead to 11,600 deaths. RCC accounts for 2–3% of all malignancies in adults and causes 2.3% of all cancer deaths in the United States annually (1 ). Approx 4% of all RCC cases are bilateral at some point in the life of the patient. Data from over 10,000 cases of renal cancer entered in the Connecticut Tumor Registry suggests an increase in the incidence of renal cancer from 1935–1989; in women the incidence increased from 0.7 to 4.2 in 100,000, and in men from 1.6 to 9.6 in 100,000 (2 ). Factors implicated in the development of RCC include cigarette smoking, exposure to petroleum products, obesity, diuretic use, cadmium exposure, and ionizing radiation (3 –9 ).