Hearing loss (HL) is a partial or total,inability to hear, It is caused by several environmental and genetic factors, and the proportion attributed to inherited causes is assumed at 50 percent, About 70 percent of cases are nonsyndromic hearing loss since hearing loss is the only symptom. To date, more than 160 genes have been identified to be associated with nonsyndromic HL. Genetic defects in GJB2 gene are the most common cause ofnonsyndromic HL.In this work, the authors detected mutations in the GJB2 gene localized on chromosome 13qll for a Vietnamese family with two children affected with nonsyndromic HL. Using PCR with specific primers, the authors could amplify all exons of the gene. Then, the PCR products were purified and sequenced. When compared with GJB2 published in GenBank with accession number NM _004004, a homozygous mutation c.235delC was found in the two children. Both father and mother are heterozygous for the mutation. The mutation is inherited ITom the parents and well known to be pathogenic, resulting in a putatively truncated GJB2 peptide p.L 79CfsX3 which leads to the loss of a functional protein in a homozygous individual. The results partly contribute to molecular studies on human inherited disorders and can be used for genetic counseling and clinical management.