Detailed information regarding follow-up of ocular adnexal lymphoma and of the frequency of large cell transformation of low-grade ocular adnexal lymphoma is limited. We studied 174 patients with ocular adnexal lymphoma (OAL) to evaluate long-term clinical outcome and patterns of failure. All lymphomas presenting with involvement of the ocular adnexa diagnosed at the Massachusetts General Hospital (MGH) between 1974 and 2007, in which at least 6 months of follow-up was available, were included in this study. There were 106 extranodal marginal zone lymphomas (MALT lymphomas, MZL), 40 follicular lymphomas (FL), 16 diffuse large B cell lymphomas (DLBCL), 5 mantle cell lymphomas (MCL), 3 small lymphocytic lymphomas/chronic lymphocytic leukemias, 1 lymphoplasmacytic lymphoma, 2 B lymphoblastic lymphomas, and 1 extranodal NK/T cell lymphoma. Relapses occurred in 42 of 106 MZL patients (40%) and in 14 of 40 FL patients (35%). Two MZL and one FL progressed to DLBCL. Five and 10-year relapse-free survival (RFS) and five and 10-year overall survival (OS) respectively were: MZL 67%, 36%, 93%, 88%; FL: 54%, 32%, 90%, 82%; DLBCL: 79%, 79% 88%, 88% MCL: 20%, 0%, 100%, 25%. MZL and FL patients often developed relapses but had long survival; progression to DLBCL was uncommon. DLBCL had a favorable prognosis. MCL had a poor prognosis.