Primary ocular lymphoma (POL), a lymphoma of the globe, is a restricted form of primary central nervous system lymphoma (PCNSL) that often progresses to the brain and meninges; frequently it is misdiagnosed until central nervous system (CNS) lymphoma develops. The optimal treatment has not yet been identified. We retrospectively reviewed the course and the treatment of POL in 31 patients. Seventeen patients were treated for isolated POL (group A) and 14 were treated only after CNS disease was diagnosed (group B). The treatment in both groups consisted of systemic chemotherapy, chemotherapy plus radiotherapy (RT) or RT alone. In group A, nine patients (53%) developed CNS progression and five (29%) had ocular recurrence. In group B, seven (50%) had CNS progression and three (21%) ocular relapse. To control for diagnostic lead time, median survival was calculated from initial ocular symptoms and was 60 months in group A and 35 months in group B (P < 0·05). Ocular lymphoma responds to a variety of therapies but treatment with chemotherapy and/or ocular radiotherapy (ORT) failed to prevent CNS progression. Patients whose ocular disease was identified and treated before CNS progression had a significantly improved survival.