Background: To study the 1-year evolution of quantitative dual-task gait parameters in comparison with single-task gait parameters and detailed neuropsychological assessment in patients with multiple sclerosis (MS) treated with natalizumab. Methods: Walking speed, stride length and stride time during a dual task (walking while forward counting, backward counting, semantic fluency, and phonemic fluency), a single walking task, and a detailed neuropsychological assessment were prospectively measured and assessed twice at the 1-year interval in 9 consecutive patients with MS treated with natalizumab. Results: Dual-task-related gait changes (walking speed, stride length and stride time while performing semantic fluency and walking speed, and stride time while performing phonemic fluency) showed a significant improvement after 1 year of treatment with natalizumab. The single walking task and detailed neuropsychological assessment did not present any modification. Conclusions: Dual-task-related gait changes using a cognitive task with a specific executive demand represent an interesting marker of disease-modifying therapy in patients with MS. © 2014 S. Karger AG, Basel.