Objective: To evaluate intradural drilling as a mechanism for the development of postoperative headache after retrosigmoid craniectomy. Study Design: A retrospective review of charts was performed on 565 retrosigmoid approaches to the cerebellopontine angle performed between January 1980 and January 1998. Patients treated with retrosigmoid vestibular nerve section without intradural drilling were compared with patients who underwent retrosigmoid removal of vestibular schwannomas in which intradural drilling was performed for exposure of the internal auditory canal. Setting: Private practice tertiary referral center. Patients: Consecutive patients undergoing retrosigmoid approach between January 1980 and January 1998 were reviewed. Main Outcome Measures: The presence of headache, duration of headache, and severity of headache were noted. Results: In this large series, 54% of patients experienced headaches after vestibular schwannoma removal, and 5% of patients experienced headaches after vestibular nerve section (p < 0.01, chi- square). Conclusions: Postoperative headache is not a characteristic of retrosigmoid craniectomy in the absence of intradural drilling. Intradural drilling is a probable cause of headache after the retrosigmoid approach. Cranioplasty is not necessary to prevent a high incidence of postoperative headache after retrosigmoid approach.