This presentation will summarize the design of the CLARION pediatric clinical trial and present initial findings on the subjects' performance with the device. A repeated measures design is used to compare each subject's preoperative performance with hearing aids to their postoperative implant performance on a battery of outcome measures. Six categories of audiologic outcome measures are administered to the subjects to achieve study end points that reflect the range of benefit predicted to occur in pediatric implant users over time. Postoperative evaluations with the CLARION are performed at 3, 6, and 12 months following initial stimulation, and semiannually thereafter. Initial findings comparing subjects' preoperative performance to their 3-month postoperative performance with the CLARION reveal improvements on all speech perception outcome measures. Performance on the outcome measures, however, is confounded by the limited cognitive and linguistic skills of some of the subjects, especially in the youngest (2- and 3-year-old) children. Information will be presented on issues inherent in the design and implementation of a large multicenter study of this nature.