Hearing loss in children under school age adversely effects speech and personality development. It is possible to improve conductive hearing loss by surgery, but difficult to improve combined hearing loss. The authors succeeded surgically improving the hearing of a 5 year-old boy suffering from speech retardation due to bilateral congenital combined hearing loss. The improvement in hearing aided speech training. He has graduated from schools for the deaf (primary, middle and senior high school). His I.Q. is 70 or less. The average hearing is in the speech range of 90 dB bilaterally, showing combined hearing loss by play audiometry. At the age of 1.5 years, he was suspected of having congenital aural atresia on the right side, congenital narrow ear canal on the left side and minor anomalies of the auricles bilaterally, including congenital aural fistulas. His mother and younger brother also suffer from bilateral congenital combined hearing loss. The tympanotomy on the left ear revealed severe anomalies, such as omega shaped ossicle composed of the malleus and incus joined to the posterior bony wall of external auditory canal and bony fixation of the stapes footplate. The bulky ossicle was mobilized by cutting the junction to the bony canal wall, and a small fenestra stapedectomy was performed. A tympanotomy on the right ear was also performed, but irregular development of the inner ear prevented the possibility of obtaining hearing improvement. The authors discussed the possibility and significance of surgery to improve hearing even in cases of profound combined hearing loss in preschool children.