This unit discusses an approach to identifying a genetic cause in an individual with nonsyndromic hearing loss. Two protocols are presented, including a full-gene sequencing assay to identify mutations in the GJB2 gene encoding the connexin 26 protein. Mutations in the GJB2 gene represent the most common cause of congenital hearing loss. In addition, a protocol to detect the presence of a 342-kb deletion that includes a portion of the GJB6 gene is presented. The GJB6-D13S1830 deletion, in homozygosity or in combination with a single GJB2 mutation, causes hearing loss. In addition to the two protocols presented, the Strategic Planning section presents a discussion of a decision-making process that can be used to begin determining which gene(s) to test for in a patient presenting with nonsyndromic hearing loss. This task can be quite challenging, with the suspected involvement of over 90 genes.