OBJECTIVE To determine whether congenitally deafened adults achieve improved speech perception when auditory and visual speech information is available after cochlear implantation. STUDY DESIGN Repeated-measures single subject analysis of speech perception in visual-alone, auditory-alone, and audiovisual conditions. SETTING Neurotologic private practice and research institute. SUBJECTS Eight subjects with profound congenital bilateral hearing loss who underwent cochlear implantation as adults (aged 18-55 years) between 1995 and 2002 and had at least 1 year of experience with the implant. MAIN OUTCOME MEASURES Auditory, visual, and audiovisual speech perception. RESULTS The median for speech perception scores were as follows: visual-alone, 25.9% (range, 12.7-58.1%); auditory-alone, 5.2% (range, 0-49.4%); and audiovisual, 50.7% (range, 16.5-90.8%). Seven of eight subjects did as well or better in the audiovisual condition than in either auditory-alone or visual-alone conditions alone. Three subjects had audiovisual scores greater than what would be expected from a simple additive effect of the information from the auditory-alone and visual-alone conditions alone, suggesting a superadditive effect of the combination of auditory-alone and visual-alone information. Three subjects had a simple additive effect of speech perception in the audiovisual condition. CONCLUSION Some congenitally deafened subjects who undergo implantation as adults have significant gains in speech perception when auditory information from a cochlear implant and visual information by lipreading is available. This study shows that some congenitally deafened adults are able to integrate auditory information provided by the cochlear implant (despite the lack of auditory speech experience before implantation) with visual speech information.