Swallowing problems can complicate the course of multiple sclerosis (MS). However, no validated questionnaire for the assessment of dysphagia in MS is currently available. We previously developed a 10-item DYsphagia in Multiple Sclerosis questionnaire (DYMUS). In the present study, this questionnaire was submitted to a validation process. Thirteen Italian MS centres took part in this research in which DYMUS was administered to 1734 consecutive MS patients during routine checkups outside relapse. The questionnaire showed very good internal consistency (Cronbach's alpha = 0.914). It was then subdivided into two subscales, both of which also showed very good internal consistency: Cronbach's alpha was 0.885 for the 'dysphagia for solids' subscale and 0.864 for the 'dysphagia for liquids' subscale. The DYMUS questionnaire was found to be an easy and reliable tool for detecting dysphagia and also for the preliminary selection of patients requiring more specific instrumental analyses, and those suitable for aspiration prevention programmes.