The author reports a case of generalized amyothophic paralysis which appeared after antitetanic serumtherapy. Neurological signs manifested together with allergic signs of the skin and realized the feature of polyneuritis. The symptomatology was both amyotrophic and motor, with no sensitive disturbs. After a bibliographical review, the author tries to explain the pathogenesis by a primary localisation of the lesion in the anterior roots of the spinal cord or in the cells of the anterior horn. Another explanation remembered by the author is the hypothesis of an allergic reaction within the muscle.