Environmental control system (ECS) is an assistive device to help the severely disabled persons to live their daily lives more independently. An 'ECS By Voice' suitable to a 54-year old C4 quadriplegic man was developed and installed in his own room for one week. The physical and psychologic impacts of the subject and caregiver were also evaluated using questionnaires including the Activity Pattern Indicator (API) and Beck Depression Inventory (BDI) before and after the application of the device. The results were as follows: (1) The voice recognition rate of the device was 97.5% in the laboratory and there was no difference in recognition rate according to the specific commanding words. (2) While using the device, both the dependency on the attendant care and the depression tendency of the subject were decreased. (3) While using the device, both caring time and depression tendency of the caregiver were decreased. We found the usefulness of ECS for the quadriplegics and the possibility of developing a Korean model of ECS which can be commercialized at a considerably less cost.