Neuroendoscopic treatment of hydrocephalic children is an established surgical modality, Open magnetic resonance imaging (MRI) technology introduces new imaging features that, in combination with endoscopy, seem particularly valuable for performing these operations. "Near" real-time production of MR images in 3 dimensions during the procedure allows real-time neuronavigation, thus, facilitating guidance of an endoscope. Additionally, intraoperative changes such as brain shift, effects of perforation, and drainage of cysts are shown during an ongoing procedure, The patency of cysts or fluid compartments inside the ventricular system can be controlled by intraoperative injection of diluted gadolinium into the cystic compartments. These new therapeutic options were applied in 2 hydrocephalic children with complex ventricular cysts: a 3-month-old girl with a large, septated arachnoidal cyst and internal hydrocephalus and a boy of 7 years, 2 months with congenital hydrocephalus and premature closure of the coronary sutures. Copyright 2002, Elsevier Science (USA). All rights reserved.