Background: Primary non-Hodgkin's lymphoma (PONHL) of the ovary is rare disease. Ovarian involvement by NHL is usually secondary, as a part of systemic disease. It is frequently diagnosed as ovarian carcinoma which causes a significant delay in diagnosis and management. Objective: To analyze, to report and to better understand the clinico-pathologic features and results of treatment, and prognostic factors of these tumors. Material & methods: This was a retrospective single institutional work that included 16 cases of primary ovarian non-Hodgkin lymphoma (PONHL) treated in National Cancer Institute-Cairo University from January 2010 till January 2015. All available medical data including the clinical and pathological characteristics, treatment, and outcomes of patients with PONHL are analyzed. Results: Data from 16 patients are obtained. The patient's age ranges from 14 to 55 years (mean 28 years). Ascites is the most common manifestation (75%). Tumor size ranges from 5 to 24 cm (mean 13.1). LDH is elevated in all cases (mean 644 U/L) and CA-125 is elevated in only 4 cases (25%) especially when there is an extensive peritoneal irritation. Ten cases (62.5%) are bilateral with stage IV-E according to the Ann Arbor staging system. The remaining six cases (37.5%) are unilateral with Ann Arbor stage I-E. There are no stage II-E or III-E in the current study. Tumors are classified according to the World Health Organization as follows: diffuse large B-cell lymphoma (10 cases) (62.5%), Burkitt's lymphoma (5 cases) (31%) and only one case of B-lymphoblastic lymphoma/leukemia. All the tumors are of B-cell lineage and are all CD20 positive. All Burkitt's lymphoma cases show higher Ki67 index (4 cases are 100% and one is 88%). The case of B-lymphoblastic lymphoma/leukemia is positive for TDT & CD 10. Surgery is the main treatment modality for primary diagnosis and for staging, although chemotherapy should have been the primary treatment because it is one of the most chemosensitive tumors. Follow-up period ranges from 3 months to 5 years (mean 33 months). Ten patients are alive without disease. Two cases experienced relapse and one case died during chemotherapy treatment. The remaining three cases died from other causes than disease. The median overall sur-* Corresponding author. H. A. Shokralla et al. 56vival time was not reached yet; however, the mean overall survival was 46.8 monthes; median progression free survival was 36 months. Conclusion: Most patients with PONHL present with symptoms attributable to an ovarian mass which necessitates extensive surgical staging that is not mandatory for lymphomas. More studies will be needed to better define and treat this rare entity.