OBJECTIVE: To evaluate the auditory outcomes of children implanted in an ear with eighth nerve hypoplasia or aplasia and to determine whether preoperative characteristics are predictive of auditory performance achieved. METHODS: Study design: retrospective case review. Setting: tertiary care medical center. Patients: ten children implanted in an ear with eighth nerve hypoplasia or aplasia, as determined by high resolution magnetic resonance imaging. Main outcome measures: Neural response test measurements, detection and speech awareness thresholds, Meaningful Auditory Integration Scale scores, as well as speech perception level achieved. RESULTS: Post-implantation, three children demonstrated little to no detection of sound, three had improved detection and awareness of environmental sounds, one developed closed-set speech perception and spoken language, and three developed open-set speech perception and spoken language. No imaging findings appeared related to outcomes. Significantly better implant detection thresholds and Meaningful Auditory Integration Scale scores were found in children who had preoperative aided auditory detection (p's=0.02-0.05). CONCLUSION: Some children with eighth nerve hypoplasia or aplasia may derive significant benefit from a cochlear implant. In our study high resolution magnetic resonance imaging was more sensitive than high resolution computer tomography in detecting neural deficiency. However, no imaging findings were predictive of auditory performance level achieved post-implantation.