This study aimed to assess mutations in GJB2 gene (connexin 26), as well as A1555G mitochondrial mutation in both the patients with profound genetic nonsyndromic hearing loss and healthy controls. Ninety-five patients with profound hearing loss (>90 dB) and 67 healthy controls were included. All patients had genetic nonsyndromic hearing loss. Molecular analyses were performed for connexin 26 (35delG, M34T, L90P, R184P, delE120, 167delT, 235delC and IVS1+ 1 A -> G) mutations, and for mitochondrial A1555G mutation. Twenty-two connexin 26 mutations were found in 14.7% of the patients, which were 35deIG, R184P, de1120E and IVS1+1 A -> G. Mitochondrial A1555G mutation was not encountered. The most common GJB2 gene mutation was 35deIG, which was followed by de1120E, IVS1+1 A -> G and R184P, and 14.3% of the patients segregated with DFNB1. In consanguineous marriages, the most common mutation was 35deIG. The carrier frequency for 35deIG mutation was 1.4% in the controls. 35deIG and del120E populations, seems the most common connexin 26 mutations that cause genetic nonsyndromic hearing loss in this country. Nonsyndromic hearing loss mostly shows DFNB1 form of segregation.