Involvement of the ovary by malignant lymphoma is a well-known late manifestation of disseminated nodal disease. Primary ovarian lymphoma is rare. We report a case of primary ovarian non-Hodgkin's lymphoma with bilateral involvement which was managed by surgery and chemotherapy. A 29-year-old woman was admitted with signs and symptoms suggestive of an ovarian cancer. Computed tomography revealed an abdominal tumor measuring 20 cm in diameter, without enlarged lymph nodes. The diagnosis of malignant lymphoma was established after bilateral adnexectomy and histological study of the excised tissue. The tumor was classified as a diffuse large B-cell lymphoma. The patient has been advised 8 cycles of standard CHOP regimen and is presently on treatment. She has now been without disease for 7 months after the surgery. According to previous reports the treatment principles and prognosis of primary ovarian lymphoma is the same as that of other nodal lymphomas.