The aims of this study were to determine the frequency and pattern of Mcm2 expression by immunohistochemistry in normal kidney (n = 10) and renal tumors [n = 56; clear cell n = 36; chromophil (papillary) n = 7; oncocytoma n = 5; and transitional cell carcinoma n = 8], compare its sensitivity to the established proliferation marker Ki-67, examine for differences in tumors derived from stable and labile epithelial cell populations in the kidney, and assess the relationship of Mcm2 proliferation to clinicopathological characteristics of kidney tumors.