Overexpression of cyclooxygenase (COX)-2 has been implicated in many pathologic conditions, including cancer. One practical inference of this finding is that sustained inhibition of COX-2 could serve as a promising target for prevention or therapy of cancer. Conventional nonsteroidal antiinflammatory drugs (NSAIDs) and recently developed COX-2-specific inhibitors have shown considerable promise in prevention of some forms of human cancer; however, its application is limited due to severe toxic side effects on normal cells. Therefore, there is a need to define novel, nontoxic dietary constituents with proven chemopreventive effects through other pathways that also possess COX-2 but not COX-1 inhibitory activity. Recent studies on green tea and its major polyphenolic constituent (-)epigallocatechin-3-gallate (EGCG) have established its remarkable cancer preventive and some cancer therapeutic effects. Here, we show that EGCG inhibits COX-2 without affecting COX-1 expression at both the mRNA and protein levels, in androgen-sensitive LNCaP and androgen-insensitive PC-3 human prostate carcinoma cells. Based on our study, it is tempting to suggest that a combination of EGCG with chemotherapeutic drugs could be an improved strategy for prevention and treatment of prostate cancer.