Despite the large number of genes that are expected to be involved in non-syndromal, recessive deafness, only a few have been cloned. One of these genes is GJB2, which encodes connexin 26. A frameshift mutation in this gene has been reported to be common in several populations and a carrier frequency of about 1 in 30 people has been detected in Italy and Spain. Mutation 35delG is difficult to detect because it lies within a stretch of six guanines flanked by thymines, so the deletion of one G does not create or destroy a restriction site and mutagenesis primers are not useful for this mutation. We have generated an allele specific oligonucleotide method that uses 12-mer oligonucleotides and easily discriminates between the normal and 35delG alleles. The method should permit a rapid analysis of this mutation in congenital cases (recessive or sporadic), including diagnosis and carrier detection of 35delG in the population.