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Introduction: Hearing loss due to mutations in the DFNB1 locus is characterized by being of pre-consecutive onset, by a degree of severity that varies generally from moderate to profound. Objective- Study deafness related to GJB2 associated with Cochlear.- Analyse results from our population Method: An rretrospective study of patients studied in the Garrahan pediatric hospital with connexin and who received a cochlear implant. Results: Despite the genotype- phenotype correlations observed, there is a significant phenotypic variability that can be the reflection of environmental factors and / or modifying genes that lead to a variable expression. Of the population studied in the Hospital (270 children), 75 patients with two connexin 26 and / or 30 mutations could be identified. Of the total of patients with mutations, 72 has bilateral profound sensorineural hearing loss and only 3 moderate to severe loss. The indicated treatment was a cochlear implant for profound losses and hearing aids for minor hearing losses. In four families, it was possible to act early when detecting in newborns the mutations present in the affected brother and in three families the presence of mutations in newborn siblings was ruled out. In homozygous 35delG patients, a hearing impairment in the first year of life with progression towards severe bilateral profound or profound hearing loss, unlike patients with a homozygous deletion in the GJB6 gene who presented a bilateral deep sensorineural hearing loss from the beginning. We have also observed that all 35delG homozygous patients showed a degree of severe to profound deafness while patients with moderate deafness had at least one non-35delG allele. Conclusion: Deafness related to GJB2 associated with Cochlear Implant is significantly better prognosis compared to the loss of acquired hearing caused by environmental etiologies. However, it was shown that the age of implantation was a better indicator of implant performance than the genotype. [ABSTRACT FROM AUTHOR]