Categories of Auditory Performance (CAP) is an index consisting of eight performance categories arranged in order of increasing difficulty. It has been used to categorize 53 children who had been deafened below the age of 3. The children were assessed by means of the CAP before implantation, and over the following 3 years. Before implantation, only 2 of the children showed awareness of environmental sounds; immediately after initial tuning, all children showed awareness of environmental sounds, and 50% showed awareness of speech sounds. Their auditory receptive abilities gradually developed over the 3-year period, and by the 3-year assessment interval, 80% were understanding phrases without lipreading, and 40% were understanding conversation. Using these data, we predict that 90% of such children will understand conversation without lipreading 5 years after initial tuning.