Immunoglobulin switch recombination is a specialized recombination event that occurs exclusively in B lymphocytes and is focused on tandemly repetitive DNA sequences called switch regions. Switch recombination occurs as an intrachromosomal deletion event in which the deleted genetic material is excised as a circle. Although the developmental profile of this recombination event is well characterized, the underlying mechanism for switch recombination is poorly understood. Recent studies detected the presence of double strand breaks in switch DNA and the dependency of switching on the Ku and DNA-dependent protein kinase proteins which are involved in repair of double strand breaks by nonhomologous end-joining. Taken together these findings strongly suggest that switch recombination is a specialized recombination system that occurs through a DNA end-joining mechanism.