A new scale for motor function measurement has been developed for neuromuscular diseases. After the study of a preliminary and a first version, the validation study included 303 patients, aged 6 to 62 years. Seventy-two patients had Duchenne muscular dystrophy, 32 Becker muscular dystrophy, 30 limb-girdle muscular dystrophy, 39 facio-scapulo-humeral dystrophy, 29 myotonic dystrophy, 21 congenital myopathy, 10 congenital muscular dystrophy, 35 spinal muscular atrophy and 35 hereditary neuropathy. The sensitivity for change was evaluated with 152 patients one year after. The scale comprised 32 items, in three dimensions: standing position and transfers, axial and proximal motor function, distal motor function. High correlations (>0.80) were found between the total score and other scores: Vignos and Brooke grades, Functional Independence Measure, the global severity of disability evaluated with visual analog scales by physicians and physiotherapists. This scale is reliable, does not require any special equipment and is well accepted by patients. It takes an average of 36 min (range 8-75) to complete the scale. Preliminary results of the second evaluation showed good sensitivity to change since last visit, considering rating by patient, investigator or physiotherapist. Also, significant differences in scores are obtained with the greatest deterioration observed in Duchenne patients.