Purpose: This retrospective study aimed to amass large data sets to enable statistical comparisons of communication outcomes for infants receiving cochlear implants (CIs) before 9 months of age compared to groups who received their first CI between 9 months and 3.5 years of age. Method: Speech perception scores and experienced clinicians' observations were used to refine the Categories of Auditory Performance Index (CAPI), thus creating its revised version, namely, the CAPI-Revised (CAPI-R). Standardized and criterion-referenced language data were used to create the novel Categories of Linguistic Performance (CLIP). The association between CAPI-R and CLIP data at two time points post implant (at 2 years of device experience and at 5 years of age) was examined in a large unselected cohort stratified for age at first implant: before 9 months (Group 1), between 9 and 12 months (Group 2), between 13 and 18 months (Group 3), between 19 and 24 months (Group 4), between 25 and 30 months Group 5), between 31 and 36 months (Group 6), and between 37 and 42 months (Group 7). Results: CAPI-R medians were 5 at 2 years of device experience, and 6 at 5 years of age. At 2 years of device experience, there was no significant difference in CAPI-R medians for children who received their first CI before 9 months compared to all other age-at-implant groups. At 5 years of age, a significantly better CAPI-R median was demonstrated by Group 1 (CI before 9 months) compared to Groups 4, 5, 6, and 7. CLIP medians were 3 at 2 years of device experience, and at 5 years of age. At 2 years device experience, and at 5 years of age, the Group 1 CLIP medians were significantly better than later age-at-implant groups. Conclusion: Median CAPI-R outcomes supported access to CIs before 18 months of age for speech perception, and median CLIP outcomes supported access to CIs before 9 months of age for optimum language development.