Non-syndromic neurosensory recessive deafness (NSRD) is one of the most common human sensory disorders. Mutations in the connexin 26 gene have been established as a major cause of inherited and sporadic non-syndromic deafness in different populations. The CX26 gene encodes the gap junction protein connexin 26 (beta-2, GJB2), whose expression was shown in several tissues and in the cochlea. The 30delG mutation is the most frequent mutation in the CX26 gene. It represents a deletion of guanosine (G) in a sequence of six Gs extending from position 30 to 35 of the CX26 cDNA. The deletion creates a frameshift resulting in a premature stop codon and a non-functional intracellular domain in the protein. The 30delG mutation can be detected at the molecular level using PCR followed by BsiYI digestion. We screened 164 mainly German patients with non-syndromic sporadic deafness for this mutation to determine its distribution in the German population. The frequency of the mutation in our analyzed patients was lower than in other studies and therefore indicates its dependency on geographically distinct populations.