BACKGROUND Cyclooxygenase-2 (COX-2) promotes carcinogenesis by inducing proliferation and angiogenesis while decreasing apoptosis and immunosuppressive activity. It is overexpressed in many malignancies including renal cell carcinoma (RCC). The aim of this study was to investigate COX-2 expression in clear cell RCC and its association with tumour grades and demographic parameters. METHODS Thirty-six clear cell RCC cases were selected. There were 21 (58.3%) men and 15 (41.7%) women with median age of 56.6 years (range: 16-74 years). Chinese constituted 16 (44.4%) of the cases; Malays 14 (38.9%) cases and Indian 6 (16.7%) cases. There were 6 (16.7%) grade 1, 20 (55.6%) grade 2, 10 (27.8%) grade 3 and none was grade 4. The paraffin embedded tissues were cut at 4 μm thick and stained with COX-2 monoclonal antibody. RESULTS Eighteen (50%) of the RCC cases were immunopositive, of which all showed strong positivity. The immunopositive cases showed cytoplasmic membrane positivity. CONCLUSIONS There was no significant association between COX-2 expression with grade, age, sex and ethnicity (p=0.457, p=0.054, p=0.389 and p=0.568 respectively). Strong positivity of COX-2 suggest that COX-2 may play a role in cell proliferation and in carcinogenesis.