A postlingually deaf patient who had been using a single-channel extracochlear implant for 5 years was reimplanted in the same ear with a 22-channel intracochlear device after electrical failure of the internal receiver. In the subsequent follow-up period, auditory performance was investigated in a series of tests with nonspeech and speech material. Two weeks after processor fitting most test scores were equal or better with the new implant. Three months later, with only minimal training, the patient's performance in sentence, numerals and vowel tests was markedly improved. Analysis of vowel confusion matrices indicated a high percentage of F2 information perceived (53% compared with 5% with the single-channel device) and somewhat less Fl information (35% compared with 4% using the single-channel device). Further improvements of speech discrimination (especially consonant recognition) are conceivable if the fine temporal resolution provided by some single-channel devices can be combined with the spectral resolution of multichannel systems.