OBJECTIVE: To conduct a pilot study in adults with the Nucleus CI24M/SP5 cochlear implant system. PATIENTS AND METHODS: Eight postlingually deafened adults who had received little or no benefit from conventional hearing aids, equipped with the Nucleus CI24M/SP5 cochlear implant system. RESULTS AND CONCLUSIONS: The results indicate that most of the subjects were able to perform well in speech recognition tests. The test performances appeared to be strongly affected by the duration of deafness. The speech processor's four user-selectable program memories have been extremely useful for the subjects to evaluate variations to the speech coding strategies in ordinary surroundings outside of the laboratory. The telemetry functions of the new implant provide a set of useful clinical and research tools for gathering greater insights into the in-situ operation of the implant.