Background: Rituximab (RTX) is increasingly used in the treatment of neuromyelitis optica spectrum disorder (NMO-SD). Administration regimen is not consensual as there is no reliable biomarker of RTX efficacy. In most cases, after induction, RTX is administered systematically every 6 months. Objective: To assess efficacy and safety of a maintenance regimen based on CD19 + CD27 + memory B-cell (mBc) detection. Methods: We conducted a study in two French centers, including patients with NMO-SD who received an induction therapy with RTX. We compared the number of administered infusions, relapses and EDSS depending on two maintenance schemes (S1: administration of 1 g RTX infusion every 6 months or S2: a scheme based on regular mBc detection. 1 g RTX was administered if mBc was >0.05%) Results: 40 patients were included (mean age: 40.2 years, F/M sex ratio: 5/1). Aquaporin-4 antibodies were positive in 75% patients. Under S1 regimen, all patients received 2 infusions per year, whereas under S2, they received 1.62 infusion per year. The mean interval between infusions under S2 was 7.4 months, without decrease of clinical efficacy. Conclusion: In our study, mBc-based administration of RTX allowed personalizing treatment administration and in several cases to lower the cumulative dose without loss of efficacy. (C) 2017 Elsevier B.V. All rights reserved.