Objective To summarize and analyze the clinical features of Hirayama disease.Methods The authors summarized the clinical data of 29 cases of Hirayama disease in recent 9 years.Resuits All of the 29 cases were male and the age of onset was 12-25 years.22 of the 29 patients only had the symptoms of one upper Jimb and7 of them had symptoms of beth upper limbs.Most of them had symptems on the right or the symptoms were on more severe in the right than left.while only one case had symmetric symptoms of both upper limbs.The arm appeared as a slope,this was due to partial muscular atrophy.EMG indicated that the impairment of spinal anterior cells were limited to the arm relevant segments and both sides were involved.Cervical MRI scan suggested spinal atrophy at the level of C5-7 vertebral bodies.being asymmetric in most of the cases.The atrophy was more obvious on the side with more severe symptoms.There was one patient whose MRI showed high T2 signal in the spinal anterior cells of the C5-6 segments.All the cases used cervical supporter and were followed up for 1-5 years.All of them had good prognosis.Conclusions Hirayama disease is more common in men with hidden onset before 20 years of age.Most of the patients noted the symptoms of hands gradually about 2 years after a period of rapid growth in height in adolescence.The predominant clinical manifestations are as follows:atrophy of lower cervical cord in cervical MRI,asymmetric spinal atrophy in horizontal impaction and the degree of atrophy consistent with the symptoms of limbs.EMG could indicate bilateral spinal anterior impairment in lower cervical cord.Rare case may present the abnormal signal in the spinal cord,but pyramid signs were absent.