Steroids have been used in the therapy of the moderate to severe forms of Graves’ ophthalmopathy (GO) and other autoimmune diseases as they act only as general immunosuppressants. Previous work has shown that blocking the CD-20 receptor on B lymphocytes has significantly affected the clinical course of GO, by rapidly reducing inflammation and the degree of proptosis. We have studied nine patients with Graves’ disease, of whom seven had active GO and two, with newly diagnosed hyperthyroidism, only mild lid signs. We also studied a group of 20 consecutive patients, treated with intravenous glucocorticoids (IVGC) according to a standard protocol. Patients treated with RTX (1000mg i.v. twice at two-week interval) and those treated with IVGC (500mg i.v. for 16 weeks) were studied monthly up to 12 months after the first drug infusion. By ophthalmological examination, GO was assessed by the clinical activity score (CAS) and by the NOSPECS score. Thyroid function and lymphocyte count were measured by standardized methods. RTX was well-tolerated and only minor side-effects were reported in 30% of patients during the first infusion. All patients attained peripheral B-cell depletion with the first RTX infusion. All but one patients showed both CD20+ cells and CD19+ cells depletion, while one had persistent 3–5% CD19+ cells in the periphery, mostly CD19+5+. Thyroid function was not affected by RTX therapy. Titers of antithyroglobulin (TgAb), antithyroperoxidase and anti-TSH receptor antibodies (TRAb) did not change significantly (P=NS) and did not correlate to CD20+ depletion (P=NS). CAS values decreased significantly (P<0.0001). Proptosis decreased significantly after RTX in both patients with active GO (ANOVA; P<0.0001) and in those with Graves’ hyperthyroidism and lid signs (ANOVA; P<0.003). The degree of inflammation (NOSPECS class 2) decreased significantly in response to RTX (ANOVA; P<0.001). In patients treated with IVGC, mean CAS value decreased significantly less than in those treated with RTX (P<0.05). Adverse effects were more frequent after IVGC (45% of patients). Seventy-five percent of patients responded to IVGC and 10% showed relapse of active GO six to eight weeks after withdrawal. The results of this study on RTX in GO suggest that the drug is effective in modifying the disease course and that the improvement of the clinical activity of GO after RTX was more significant than after IVGC. We did not observe relapse of active GO, even after B-cell return in peripheral blood. This might be related to the persistence of a significant degree of B-cell depletion after RTX observed in the peripheral blood as late as two years of follow-up. RTX therapy was also effective in improving proptosis and soft tissue inflammation. The mechanism by which RTX affects GO is unknown. It may act as a true immunosuppressor by switching off reactions inducing the active phase of TAO, perhaps by influencing the cytokine production in the orbit or by inducing depletion of antigen presenting B-cells.