Ocrelizumab (anti-CD20) that targets B-cells was given as two treatment cycles, 6 months apart, in a phase 2 study in relapsing-remitting MS. It reduced MRI activity by ~90% (median T1 Gd-lesions at wk 24: placebo 1.6, 600mg 0.0, 2000mg 0.0, Avonex 1.0; p<0.0001 vs placebo) and annualised relapse rate by up to 80% (ARR: placebo 0.61, 600mg 0.18 (RRR 80%), 2000mg 0.2 (RRR 72%), Avo 0.4). Importantly the overall adverse event profile looks good (AEs: placebo 70%, 600mg 61%, 2000mg 65%, Avonex 55%). Infusion reactions typically disappeared at the day 15 infusion and there were no opportunistic infections. Worryingly there was one death in the high dose Ocrelizumab group at 14 weeks, from "systemic inflammatory response syndrome". These very impressive results need to be tempered against the death that we must assume is due to Ocrelizumab. Nevertheless this study demonstrates the importance of B cells in the pathogenesis of MS; the latter needs further exploration and may ultimately lead to a safer and even more effective therapy.