Although the treatment of colloid cysts remains controversial, high viscosity and small volume are poor prognostic indicators for successful burr hole aspiration and cortical incision via craniotomy may be associated with postoperative epilepsy. The anterior transcallosal approach provides a direct and adequate pathway to the lateral ventricles, where the foramen of Monro serves as a natural entrance into the anterior third ventricle, especially when the foramen is dilated by a lesion. When the midsuperior portion of the IIIrd ventricle cannot be reached, the interforniceal or the subchoroidal exposures have been advocated. Stereotactic techniques contribute to a minimal invasive approach and reduce morbidity. Nine patients harbouring anterior third ventricular cysts (seven colloids and two intrinsic craniopharyngiomas) underwent anterior transcallosal microsurgical excision assisted by an interactive infrared-based image guided system (EasyGuide, Neuro, Philips). There were 4 men and 5 women ranging in age from 15 to 42 years (mean 28.5). Transcallosal transforaminal (5 cases) or interforniceal (4 cases) approaches allowed total excision in eight patients and subtotal in one. Postoperative morbidity included a case of transient hemiparesis and a case of transient short-term memory disturbances; both resolved in the first months. Mortality was zero. Particular advantages of the method were accurate trajectory and position of callosotomy incision determination, visualisation and avoidance of superior saggital sinus, retraction of bridging veins and the often variable pericallosal arteries, spatial orientation within the ventricular system, and identification of the periventricular anatomical structures.