The retrosigmoid approach, also known as the retromastoid approach, is the universal approach for the microneurosurgical management of the lesions of the cerebellopontine angle. This chapter outlines the stages of the retrosigmoid approach and also some specific accesses (transmeatal, suprameatal, and safe entry zones to the brainstem). While the retrosigmoid approach is based exclusively on anatomical references, some intraoperative aids are helpful, particularly neurophysiological monitoring. Although uncommon, complications are possible, including venous thrombosis, recurrent headaches, and cerebrospinal fluid fistula.