An implantable hearing device through temporal bone was first introduced in 1985. Recently, the authors used ABC (Audiant Bone Conductor ; implantable bone conduction hearing device) for 2 patients, who was the one of bilateral congenital external canal atresia with microtia the other was the one of external canal defects following bilateral radical mastoidectomy. We observed following good results without any complication in these patients, now report these experiences with a brief review of literature. The results were as follows : 1) The average threshold difference between bone conduction and hearing with ABC stimulation was about 6dB in the speech frequencies (500 Hz, 1,000 Hz and 2,000 Hz). 2) As on conventional hearing aid use, there was a more favorable loudness gain in the high frequencies than in the low frequencies. In the frequencies of 2,000 Hz and 4,000 Hz, overclosures were observed. 3) By using ABC, we might expect the CROS effect on the patient of ipsilateral SNHL.