Bone-conducted ultrasounds (BCUs) can be perceived by the profoundly deaf, who hardly sense sounds even with conventional hearing aids, as well as normal-hearing subjects. A bone-conducted ultrasonic hearing aid (BCUHA) was developed for the profoundly deaf. With the BCUHA, ultrasounds at about 30 kHz are amplitude-modulated by speech sounds and presented to the user's mastoid by a vibrator, and users can perceive demodulated speech sounds. The basic parameters of the BCUHA were determined from the results of our former studies of the characteristics of BCU perception. Psychoacoustical tests were carried out to evaluate the utility of the BCUHA. The results showed: (1) more than 40% of profoundly deaf subjects were able to perceive sounds and 17% were able to recognize words using BCUHA; (2) articulations for Japanese monosyllables were about 60%; and, (3) intelligibility for familiar 4-mora Japanese words reached 80%. These results indicate the practicability of BCUHA.