The post-polio syndrome refers to new neuromuscular symptoms developed by some patients many years after recovery from acute poliomyelitis. Several groups were separated: musculo-skeletal symptoms (different from a new spinal cord disease), infraclinical signs (EMG), post-polio muscular atrophy (new lower motor neuron objective signs) with several subgroups: cramps and fasciculations, benign focal weakness and atrophy (in previously affected muscles or in unaffected muscles), progressive spinal muscular atrophy. The following examination were performed in some cases, but not all, in this retrospective study: muscle CT scan, conventional electromyography (EMG), quantifying-EMG, macro-EMG and single-fiber EMG. The serum titers of neutralising antibodies to polio virus type 1, type 2 and type 3 were negative. No oligoclonal bands were found in the CSF from 6 patients screened by electrophoresis immunoelectrophoresis. Serum creatine kinase or aldolase was high in 6 patients. The same unusual features in this syndrome were observed on muscle biopsies: muscular hypertrophy and interstitial eosinophils; two patients had rimmed vacuoles in the muscle fibers.