The GJB2 gene defects are the most frequent cause of autosomal recessive non-syndromic hearing loss (DFNB1). Epidemiological data suggest that 35delG is the most prevalent mutation found in 88% of mutated alleles. Another mutations - 313del14 was found in 7% of mutated alleles. The other mutations were identified only in single families. Following the analysis of distribution of GJB2 mutations in the Polish population we propose an algorithm for molecular diagnosis of DFNB1. We propose to screen all patients affected with prelingual non-syndromic deafness for 35delG mutation using ASO or multiplex AS-PCR methods. The presence of 35delG on two alleles confirms DFNB1. The identification of heterozygous 35delG mutation requires additional GJB2 analysis including 313del14 mutation detection and en exon 2 direct sequencing. To determinate the frequency of digenic (GJB2/GJB6) background of DFNB we screened 17 patients with heterozygous 35delG mutation for deletion of 342 kb in GJB6 gene. No such mutation was detected in the analyzed group.