We have been introducing the intermittent positive pressure ventilation (IPPV) therapy in Duchenne muscular dystrophy (DMD) since 1990. Then, the changes of life-span and causes of mortality by IPPV were investigated in this study. The subjects were 157 patients of long-term followed up DMD in our hospital. The Kaplan-Meier's survival curve of 73 IPPV treated patients showed a median survival time of 31.0 years of age, whereas that of 20.4 years in 84 patients not treated by IPPV. The actual mean age of death in 29 IPPV treated patients was 25.68 +/- 5.18 years-old (M +/- SD), which was significantly higher than that in 74 patients with not-IPPV treated of 19.76 +/- 3.47. The IPPV treatment changed the major causes of death; 59.5% to 3.5% for respiratory failure, 12.2% to 37.9% for cardiac failure, and 0% to 10.3% for repiratory trouble. There were certain number of patients who died of repiratory infection, respiratory tract disorder, digestive organ disorders and sudden death. Thus, IPPV therapy is significantly effective for prolongation of life-span in DMD, and it seems to be necessary to establish the treatment strategy for cardiac failure and other potentially fatal complications.