Introduction: Although many physiological and anatomical studies of the efferent system have been carried out, its functional role is not fully understood. Sectioning of the vestibular nerve could thus create an experimental model for further in-depth study of this system. Chinchillas have a large bulla and a thin temporal bone, making posterior fossa surgery an attractive option. Objective: A surgical approach used in live chinchillas is described with detailed anatomy of the medial portion of the temporal bone. This study has an objective to facilitate experiments in the neuro-otology fields. Methods: Eight male chinchillas laniger, weighing from 500 to 750g, were submitted to surgery. Occipital osteotomy was performed without damage or isolation of the sigmoid sinus and the vestibular nerve was sectioned without invading the internal acoustic meatus. Results: There were no complications, and the cochlear and facial nerves were perfectly preserved, as verified in postmortem control. Conclusion: This surgical approach allowed safe and successful sectioning of the vestibular nerve with shorter duration of surgery and less manipulation of the brain stem.