Image-guided neurosurgery is an important development in the management of brain tumours. Intra-operative imaging is an extension of this modality. It is important because it compensates for brain shift, allows accurate navigation, and gives verification of what has been done surgically before the patient leaves the operating room. It extends the capacity of image-guided surgery significantly. This paper describes the use intra-operative imaging using MR for brain tumour surgery, the devices presently available for doing this, and potential future applications of intra-operative imaging. It describes in some detail the specific indications for intra-operative imaging including biopsy, resection of intra-axial tumours, and identification and resection of some extra-axial tumours. The description includes the advantages and disadvantages of using intra-operative MRI in this setting.