In recent years the quality of ultrasound (US) imaging has improved considerably. The integration of three dimensional (3D) US with neuronavigation technology has created an efficient and inexpensive tool for intra-operative imaging in neurosurgery. Our experience is based on more than 900 operations with the intra-operative 3D ultrasound equipment SonoWand® and some operations with the research equipment Custux X. The technology has been applied to improve surgery of intraparencymal brain tumours, but has also been found to be useful in a wide range of other procedures, such as operations for cavernomas, skull base tumours, medulla lesions, arteriovenous malformations (AVMs) and for endoscopy guidance. Compared to intraoperative magnetic resonance imaging (ioMRI), 3D US technology is advantageous in different ways: it is flexible and can be used in any operation theatre. There is no need for special instruments, and no need for radiologists or technicians. It adds very little extra time to the operation, and the investment-costs are considerably lower than for ioMRI.