Renal cell carcinoma is the most frequent renal epithelial tumor having various subtypes differing in their prognosis and therapeutic response. In most cases it is possible to distinguish subtypes on the basis of histology alone, however, there are diagnostic difficulties for the tumors having granular/eosinophilic cells which create morphologic similarities not only between the subtypes of renal cell carcinoma, but also, between a benign tumor and renal oncocytoma. To achieve correct diagnosis, immunohistochemical analysis focused on cytokeratin (CK) proteins has been used increasingly. We examined the diagnostic utility of CK7, CK10, and CK20 in the classification of renal epithelial tumors based upon an immunohistochemical analysis. The study included tissue macroarray (4 mm) blocks of 83 renal cell carcinomas (62 clear cell, 6 chromophobe, 13 papillary, 2 unclassified subtype), and 6 renal oncocytomas. Fuhrman nuclear grade of the tumors, divided into low (grades 1, 2) and high nuclear grade (grades 3, 4) was negatively correlated with CK7 expression (p=0.001). Diffuse and significantly higher CK7 expression was found in “non-clear cell” (chromophobe and papillary) subtypes than in clear cell renal cell carcinomas (p=0.001). Of 6 renal oncocytomas, 4 was focally positive for CK7. The results demonstrate that, diffuse and strong CK7 immunoreactivity supports the diagnosis of “non-clear cell” subtype versus clear cell renal cell carcinoma and renal oncocytoma. Seldom CK20 reactivity of the tumors did not show any significance, and the tumors were totally unreactive to CK10 which eliminates diagnostic utility of CK20 and CK10 in the classification of renal epithelial tumors.