Ovarian involvement as an initial manifestation of lymphoma, without detectable extraovarian disease, is a rare occurrence. The diagnosis of ovarian lymphoma is almost invariably unsuspected until the tumor has been examined histologically. A 25-year-old null gravid woman presented with abdominal distension. Presence of abnormal lymphoid cells in pleural effusion led to presurgical assumption that the pelvic mass noted on computerized tomography examination might be an ovarian lymphoma. We performed left salpingo-oophorectomy. Clinical, histologic, and molecular examination revealed Burkitt's lymphoma of the ovary with c-myc gene rearrangement and mRNA expression of multiple cytokines. She received dose-intensified combination chemotherapy. She is alive and free of disease 30 months after the diagnosis. Immunophenotype and molecular findings allowed reliable discrimination of Burkitt's lymphoma from diffuse large B-cell lymphoma and other lymphomas. If an ovarian tumor is solid and suspected to be of lymphoid origin, we suggest that it is necessary to obtain samples for genetic examination at surgery. This strategy often provides important information to establish therapeutic regimen and predict patient prognosis.