The researchers evaluated the contribution of cochlear implants (CIs) to speech perception by a sample of prelingually deaf individuals implanted after age 8 years. This group was compared with a group with profound hearing impairment (HA-P), and with a group with severe hearing impairment (HA-S), both of which used hearing aids. Words and sentences were presented to the auditory channel alone, the visual channel alone, and the combined auditory-visual channel. Some of the results indicated better performance of the CI group than the HA-P group, thus indicating the advantage of CIs over hearing aids for "late" implantees, especially under difficult listening conditions. In addition, all participants relied on visual information under difficult auditory conditions. These last outcomes suggest that intervention with CI users should include exposure to visual as well as auditory information and should emphasize auditory-visual integration. (Contains 3 tables and 3 figures.)