Abstract INTRODUCTION Navigated 3D-ultrasound (nUS) is a powerful and multi-purpose adjunct during tumor resections. We review our cumulative results in a dedicated neuro-oncology service spanning a six year period, highlighting its role in glioma surgery. METHODS Since 2011 we have been used a navigated 3D ultrasound system for intraoperative image guidance during brain tumor surgery in 300 cases. A prospectively updated database was queried to retrieve demographic, clinico-radiological and pathological details. Specifically, we evaluated the utility of the IOUS in different setups and assessed its predictive accuracy and impact on extent of resection (EOR) as well as survival in gliomas. RESULTS >300 (204 males/96 females) brain tumors were operated [197 high grade gliomas, 28 LGG, 24 Meningiomas, and 51 other tumors]. Radical resection/debulking was intended in 270 (90%). In 30 (10%), only frameless biopsy was performed. The US was intended for resection control in 219 (73%) tumors, most of them being intrinsic gliomas. Intermediate scans prompted further resection in 101 cases (46%). A final resection control scan was performed in 176 cases (confirming complete excision in 99, and residual tumor which could not be further resected in 77). The nUS was a very useful tool in tumor surgery, providing a good diagnostic accuracy (85-90%) in predicting tumor residue. It also helped us improve the EOR in malignant gliomas as well as non-enhancing gliomas. In the subset of resectable tumors, the gross total resection rate was 88%. Further, in a small subset of malignant gliomas, we demonstrated that it helps extend tumor resection beyond the contrast enhancement zone. In GBMs, in a multivariate model, use of the nUS was an independent predictor of survival. CONCLUSION Considering the ease of use, widespread accessibility and low-cost nature, IOUS can be a potentially useful adjunct during a range of neurosurgical procedures, especially tumor resections.