Num-chin syndrome', isolated mental neuropathy, is a rare manifestaion of malignant hernatologic diseases, but important sign for early diagnosis and prediction of clinical course and prognosis. Here we report 7 cases of numb-chin syndrome; one in leukemic transformation of malignant lymphoma, one in blastic crisis of chronic myelogenous leukemia and 5 in acute leukemia Two cases of acute leukemia revealed the 'numb-chin sign' in early course of disease before the diagnosis of leukemia and other three in aggravating state of acute leukemia. The therapeutic response and prognosis was poor and 5 cases expired in a few months.