Eight cases of Myositis Ossificans observed in paralytic patients were studied. The original lesions leading to the paralysis were Cord Injury(4), C.V. A.(2), and Coma of various causes(2). The results were as follows; 1) In half of all, the occurrence of the ossification ranged between 3 and 4 weeks after the initiation of passive exercise. 2) The most frequent site of the lesion was the paraarticular area. 3) To cessation of passive exercise the lesion responded with prompt decrease in size. 4) It seems that as in normal ossification the repair process of aseptic inflammation derived from the bleeding or the hematoma formation may be the main etiological factor of this lesion in paralytic patients whom the passive exercise were forced.