Whether muscle strength deteriorates with time in spinal muscular atrophy (SMA) types II and III is still debated. We present a long-term follow-up study on muscle strength in 30 patients with SMA types II and III. Median follow-up time was 17 years. Median number of assessments was four. All patients were assessed by Manual Muscle Testing (MMT), Brooke upper limb scale and EK scale. There was a difference in muscle strength of the upper limbs from first to last assessment in SMA II (p