Background <p>In amyotrophic lateral sclerosis (ALS), progressive weakness makes walking practice increasingly unsafe and difficult, accelerating loss of mobility and autonomy. Lower-limb exoskeletons could preserve task-specific stepping in a controlled setting, but evidence in ALS remains scarce. This study evaluated the safety of an intensive Atalante exoskeleton gait-training program and explored its effects on walking and related clinical outcomes.</p> Methods <p>In this prospective, monocentric ABA pilot study, 10 ambulatory persons with ALS underwent three consecutive 6-week phases over 18 weeks: A1 (baseline, usual care), B (intervention: Atalante exoskeleton gait training added to usual care; 18 sessions, 3 times/week), and A2 (withdrawal, usual care), with repeated assessments every 3 weeks. The primary endpoint was safety, assessed by adverse events (AE). Secondary endpoints included ALS Functional Rating Scale-Revised, forced vital capacity, standardized walking tests (6-minute walk test, 10-meter walk test, Timed Up and Go test), Berg Balance Scale, postural control on a force platform, lower-limb strength with dynamometry, spasticity with isokinetic dynamometer, Fatigue Severity Scale, Modified Fatigue Impact Scale, ALS Assessment Questionnaire-40, and Hospital Anxiety and Depression Scale. Exoskeleton-specific patient-reported outcomes (PROs) included intrinsic motivation, participants’ attitudes toward the intervention, perceived subjective impact of the training, perceived efficacy and interactivity of the exoskeleton. The results were analyzed with linear mixed-effects models.</p> Results <p>No serious AE occurred, and one mild AE was certainly related to the intervention. No outcome showed significant phase-specific slopes or slope contrasts, although several measures displayed directionally consistent trends compatible with attenuated decline during phase B and a return toward a less favorable trajectory after withdrawal. Exoskeleton-specific PROs indicated high intrinsic motivation and acceptability (usefulness for standing, perceived safety, ease of participation, and ease of installation/uninstallation rated very highly), with perceived gait-training efficacy generally positive. Participants frequently reported reduced immobility and increased accomplishment (80% each) and postural improvement (70%), and the Net Promoter Score of recommendation was + 40.</p> Conclusions <p>Atalante exoskeleton gait training was safe and feasible in ambulatory ALS. These pilot data can guide the optimization of future studies to test whether it preserves function.</p> <p><i>Trial registration</i> ClinicalTrials.gov, NCT06199284. Registered on 29/12/2023.</p>