To study the benefit of the application of a bone-anchored hearing aid in patients with a unilateral air-bone gap. Prospective evaluation in eight patients. Binaural hearing was assessed in the sound field by comparing aided and unaided scores obtained with a sound localization test and a speech recognition in noise test with spatially separated sound and noise sources. Tertiary referral center. The patients had subnormal hearing and unilateral conductive hearing loss. Sound localization improved significantly in the six patients with acquired hearing loss. The binaural advantage, studied with speech-in-noise tests with spatially separated speech and noise sources, proved to be comparable with that in a control group of subjects with normal hearing when they were listening monaurally versus binaurally. For one of the two patients with unilateral congenital conductive hearing loss, the results were ambiguous. This patient's age at the time of surgery was high: 40 years (the other patient was 19 years old at the time of surgery). This might have played a role. If reconstructive surgery is not possible (e.g., in a patient with a chronically draining ear or a severe congenital malformation), a bone-anchored hearing aid is an option to reestablish binaural hearing. The results reported herein suggest that, at least for patients with acquired hearing loss, the bone-anchored hearing aid is an effective treatment of unilateral conductive hearing loss.