BACKGROUND Lesions located deep within the frontal and parietal lobes adjacent to the internal capsule are often considered surgically inaccessible. We have used intraoperative stereotactic lesion localization in conjunction with microsurgical dissection of the lateral sylvian fissure to accurately and atraumatically approach such lesions through the insular cortex. METHODS When possible, the sylvian fissure is widely opened using standard microsurgical technique. However, exploration through a precisely placed exposure no more than 1.0 cm in length is still feasible. Repeated intraoperative lesion localization employing ultrasound, frame-based or frameless stereotaxis was used to guide dissection deep to the Insular cortex. RESULTS Using this approach we have resected five cavernous angiomas, three plexiform AVMs and 2 low-grade gliomas. There was a single case of transient dysphasia in seven dominant hemisphere explorations and a single case of transient somatosensory impairment. Otherwise, there were no new transient or permanent postoperative neurologic deficits. In two cases, hemiparesis present prior to surgery improved following resection of a cavernous angioma. CONCLUSIONS The transsylvian, transinsular approach can be employed to safely expose lesions deep within the cerebral hemisphere. Anatomic considerations, surgical technical refinements, and clinical results are the subject of this report.