Renal cell carcinoma accounts for approximately 3% of adult malignancies and 90-95% of neoplasms arising from the kidney. Renal cell carcinoma has a male-to-female preponderance of 1.6:1 and it commonly occurs in the fourth to sixth decades of life, but the disease has been reported in younger people who belong to family clusters (Sachdeva et el., 2008). Cyclooxygenase -2 catalyses the synthesis of prostaglandins from arachidonic acid. There is ample evidence to suggest an important role for COX-2 in cancer formation (Hashimoto et al., 2003). Retrospective study including retrieval of formalin fixed paraffin embedded tissue sections from archival blocks of thirty cases of renal cell carcinoma were collected from the Department of Pathology-Cairo University and private laboratories in the period from May 2005 up to February 2007. This thesis consisted of introduction, aim of work, review of literature, material and methods used, results illustrated by images, discussion of results, conclusions, recommendations and list of references, together with a summary in English and another in Arabic. Immunohistochemical staining of COX-2 (Cyclooxygenase-2) was done using the streptavidin-biotin technique.This work reveals that COX-2 is positive in almost all cases of renal cell carcinoma (29/30) and negative in only one case. An association was found between COX-2 expression and some clinicopathological features, including tumor size, and tumor grade while there were no relationship between COX-2 expression and age, sex of patient and histological type and stage of tumor.