This paper reports the results of a Consensus Development Conference on Cochlear Implants sponsored by the National Institutes of Health to improve the hearing of children and adults with hearing impairments. The following questions are addressed: (1) Who is a suitable candidate for a cochlear implant? (2) What are the advantages and disadvantages of the different types of cochlear implants? (3) How effective are cochlear implants? (4) What are the risks and limitations of cochlear implantation? (5) What are the special considerations for children? and (6) What are the important directions for future research? The paper points out the importance of considering audiological, electrophysiological, medical surgical, psychophysical, psychological, and linguistic criteria in selecting suitable candidates. It outlines features of intracochlear, extracochlear, single channel, multichannel, feature-extraction, and non-feature-specific systems. The difficulty in predicting the outcome for a particular person is emphasized, but general expectations are suggested. Risks involved in cochlear implantation include medical complications, interference with residual hearing cues from the other ear, and possible corrosion of platinum electrodes. Limitations, such as refraining from contact sports, are also noted. Discussion of special considerations for children focuses on criteria for success, the minimum trial period, long-term prosthesis-tissue interactions, and other factors. Members of the consensus development panel are listed. (JDD)