We investigated the clinicopathologic characteristics of 17 patients (13 men and 4 women) with primary orbital malignant lymphoma using the Working Formulation. Most of the cases belonged to the low-grade malignancy group, and more women than men were in the histologically high-grade malignancy group. The phenotype of the tumor cells was investigated immunohistochemically. All cases showed the monoclonal feature of a B-cell lineage. All patients received chemotherapy with or without radiotherapy. Of 16 subjects, 15 achieved a complete remission; none of these patients has had a recurrence since the completion of the initial therapy (range of follow-up from 16 months to 10 years). One patient died.