An interventional pilot study to assess the tolerability and activity of the intralesional injection of rituximab, a chimeric mAb that targets the CD20 antigen, in patients with orbital B-cell lymphoma. Five patients received four intralesional injections (one injection a week) of rituximab together with ropivicaine 2%. Side-effects and tumor response were assessed after each injection and during the follow-up (20 months). Two patients obtained complete remission of the intraorbital lesion. Two patients showed incomplete response after induction therapy and received planned escalating rituximab doses, obtaining regression of subjective symptoms. One patient did not achieve tumor regression after the first injection and underwent systemic treatment. This small exploratory study suggests that intralesional rituximab is a well-tolerated treatment for patients with primary ocular adnexal lymphoma. These preliminary findings suggest that intralesional rituximab is a well-tolerated strategy in anterior intraorbital lesion localization of lymphoma. (Cancer Sci 2011; 102: 1565–1567)