OBJECTIVES: Unilateral cochlear implantation is generally accepted as a cost-effective intervention for hearing impaired patients. They gain understanding in quiet conditions, but report difficulties with sound localization and in noisy conditions. These can be solved with bilateral implants. Currently in Spain, there are estimated to be about 350 bilateral cochlear implanted patients.Our objective is to perform an economic evaluation of bilateral cochlear implantation in adults and children. METHODS: We reviewed the published literature to find the effectiveness of bilateral cochlear implantation, and costs of the intervention, to estimate the incremental cost-effectiveness ratio.Our model only considers costs for public systems described by the literature.The time horizon considered is the remaining life of receipients.We use a discount rate of 3% in future costs and effects. Conditions under which bilateral cochlear implants could be cost-effective were explored. RESULTS: In adults we find that bilateral cochlear implantation varies from €53,018/QALY when intervention is simultaneous up to €63.487/QALY, in the case of sequential mplantation. In children these ratios show more efficiency, from €44,199 to €56.640/QALY, due to the longer time they can benefit from implants. CONCLUSIONS: Patients who already have hearing in one ear can obtain advantages from Bilateral cochlear implantation. It improves their spatial localization of sound and their hearing in noisy circumstances, but it has limited impact on quality of life measured as QALYs. Subsequently the incremental cost-effective ratio is higher than usually accepted in public health systems.