Lymphoma is a malign disease of the lymphoid system. A variety of risk factors have been described in pathogenesis of disease. We investigated the role of Cyclooxygenase-2 (Cox-2) in malign lymphomas. A total of 52 patients who were admitted to the Oncology Unit of Mersin University with histologically diagnosed lymphoma were enrolled to this study. Ten of the patients had Hodgkin's disease (HD), and 42 had non-Hodgkin's lymphoma (NHL). An immunuhistochemical method was used for Cox-2 expression. Cox-2 expression was detected in 24 of the 42 patients (57%) with NHL, and it was found in seven of the 10 patients (70%) with HD. The mean patient age expressing Cox-2 was 50.2 +/- 16.6 years and 48.0 +/- 15.5 years for patients without Cox-2 expression. This difference was not statistically significant (P = 0.660). The overall survival of Cox-2-positive patients was less than for those without Cox-2 expression but the difference was not significant statistically (16.4 +/- 11.4 vs. 14.7 +/- 8.2 months, respectively, P = 0.552) in NHL. There was a correlation between Cox-2 and stage of disease. As the stage increased the Cox-2 expression increased (P = 0.037) in NHL. The complete response rate to therapy was significantly higher in Cox-2-negative patients than the Cox-2-positive group (70.6% vs. 20.8%, respectively, P = 0.001) in NHL. There was no correlation between Cox-2 expression and IPI score, extranodal involvement, tumor grade, and B symptoms. Our findings demonstrate that there is a clinical correlation between the Cox-2 expression and prognostic factors in lymphoma patients. The combination of Cox-2 inhibitors with standard chemotherapeutics may enhance the potential of treatment options for malign lymphomas.