Eighteen patients with a 22-channel cochlear implant were evaluated both pre- and postoperatively with vestibular function tests; caloric test and body balance test using stabilometry. Preoperative promontory stimulation results and postoperative psychophysical factors of the cochlear implant showed no correlation with the preoperative vestibular function test results. The results of speech perception tests were not affected by the degree of residual vestibular function in any of the patients. However, for patients with deafness for a period of 10 to 20 years, the degree of the residual vestibular function estimated by the caloric test showed a correlation with the results of speech perception tests, significantly in the consonant recognition score. The results, not of length or the Rombberg ratio, but rather of the area of body sway, showed a correlation with the results of speech perception tests; consonant recognition, in patients with a short duration of deafness. Therefore preoperative vestibular function results may be useful as a predictive factor in postoperative speech perception; consonant recognition, for patients with a short duration of deafness. Reduced results of caloric testing after surgery were found in one of 11 patients (9%) with residual vestibular function. The occurrence of vertigo immediately after surgery was observed in 5 of 18 patients (28%), but this symptom was transient. No change in stabilometry results, pre-versus post-operatively, was observed. Thus, vestibular damage after surgery was considered to be minimal.