BACKGROUND The orbit is rarely a secondary site of lymphoma dissemination, and only few reports exist on the course and characteristics of involvement in these sites. METHODS The authors retrospectively reviewed the records of 187 consecutive patients with systemic non-Hodgkin's lymphoma (NHL) diagnosed and treated at Beilinson Medical Center between 1986 and 1992. RESULTS Ten patients (5.3% of those with NHL) had orbital or adnexal involvement or both. Histologically, six had intermediate-grade lymphoma, three had diffuse small cleaved cell lymphoma, and one had nodular small cleaved cell lymphoma. In all 10 patients, the lymphoma was widespread, and in 6, there were two or more other extranodal sites of involvement, mainly, bone marrow (six) and skin (three). The orbital involvement was found either at presentation or as late as 53 months after primary diagnosis. Various therapeutic approaches were chosen, from local orbital irradiation to different mild to aggressive chemotherapeutic protocols. Complete regression of the orbital or adnexal involvement or both was observed in 9 of 10 patients, but in 6 the systemic disease either persisted or recurred at other sites. CONCLUSIONS Orbital or adnexal involvement or both by NHL may appear at any time during the course of the disease. It responds well to either chemotherapy or radiation therapy with prolonged local remission. The results of this study strongly suggest that every patient with NHL in whom any periorbital or orbital mass, ptosis, proptosis or lid edema develops should be suspected of having orbital lymphoma involvement until proven otherwise.