Clinical introduction of implantable ventricular assist devices (VADs) is expected to encourage VAD therapy for severe heart failure patients in Japan. Since even minor device malfunctions can lead to serious outcomes in these patients, it is very important to collect and analyze data on device malfunctions occurring during their use at home. This study was undertaken to collect and analyze such data from 9 patients with implanted VADs (EVAHEART™, 4 patients; Jarvik2000, 3 patients; Duraheart™, 2 patients) living at home, within the framework of a clinical trial carried out at our hospital. During the home stay period of 449 ± 253 days (range 12-801 days, total 4044 days), the total number of device malfunctions was 31 (0.31 events/patient/year). Those with EVAHEART™ were Cool-seal system-related (9 events) and battery-related (6 events) malfunctions. Those with Jarvik2000 were battery-related (7 events), alarm (1 event) and uncertain cause (1 event) malfunctions. Those with Duraheart™ were battery-related (3 events), alarm (3 events) and other component (1 event) malfunctions. Although the incidence was not very high and none of these device malfunctions led to cessation of blood pump operation in this study, it is necessary to establish a communication system for properly obtaining detailed information in the event of serious device malfunctions. Furthermore, establishment of a home-living-patient support system covering extensive areas is urgently needed, since this can facilitate rapid action to deal with serious device malfunctions.