Ocular adnexal lymphoproliferative lesions consist of a spectrum of disease entities, including reactive lymphoid hyperplasia, atypical lymphoid hyperplasia, and lymphoma. No clinical or radiologic criteria facilitate a distinction among these lymphoproliferative lesions. The two hyperplastic processes may evolve to localized or systemic lymphoma. A similar pattern is evident in other mucosa-associated lymphoid tumors elsewhere in the body. Most ocular adnexal lymphomas are small lymphocytic non-Hodgkin's tumors with an indolent course; frequently, they remain localized to the ocular adnexa. In comparison, intermediate- and high-grade lymphomas are less common in the ocular adnexa but more aggressive. An approach to the diagnosis and treatment of these complex entities is suggested. Despite new pathologic classification schemes, immunophenotypic labeling, and molecular genetic analysis, the prognosis for patients with small-cell lymphoma in the ocular adnexa is difficult to predict.