Because the outcome of patients with primary ovarian non-Hodgkin's lymphoma (NHL) is controversial, we present the incidental finding of a primary malignant lymphoma of the ovary in a 50-year-old patient. Three and a half years following ablative surgery and adjuvant chemotherapy, the patient is alive and disease free. Ovarian lymphoma is a disease of reportedly poor prognosis. However, many previously reported cases of ovarian lymphoma actually represented ovarian involvement by a more diffuse lymphomatous process. If stringent criteria are used for case selection, true primary ovarian lymphoma is a very rare disease and usually carries a favorable prognosis.