Abstract BACKGROUND The intraoperative MRI (iMRI) at Sahlgrenska University Hospital installed in 2017 was the first introduced in Sweden. Herein, we present a single center study with our observations from the first 100 patients undergoing neurosurgery in the dedicated iMRI surgical theater. METHODS Patients undergoing surgery in the 3T iMRI hybrid surgical theatre at our neurosurgical department between December 2017 to May 2021 were included after informed consent. Demographic, clinical, surgical, histological, radiological and outcome parameters, as well as variables related to iMRI, were retrospectively collected and analyzed. Patients were subdivided into adult and pediatric cohorts. RESULTS A variety of neurosurgical procedures were performed; resection of tumors and epileptic foci, endoscopic skull base procedures including pituitary lesions, deep brain stimulation (DBS), laser interstitial thermal therapy (LITT) and biopsies. Mean age was 32 years (range 0-81 years), 41 patients were pediatric and 42% were female. An iMRI scan was carried out in 96% of cases and led to continuation of surgery in 50 percent of cases, mainly due to visualized remaining pathological tissue. Median time to iMRI from intubation was 280 minutes and median total duration of surgery was 445 minutes. The majority of patients experienced no postoperative complications (70%), 13 patients suffered permanent postoperative deficits, predominantly visual. CONCLUSION We demonstrate demographics, clinical, surgical and radiological variables from the first 100 patients planned for surgery in the iMRI surgical theatre after INTRODUCTION in 2017. We found that iMRI was performed in almost all cases. In the pediatric cohort, tumors and epileptic focus were main indications for surgery. In adults, indications were intrinsic brain tumors, transsphenoidal pituitary tumor and DBS. Utilization from a resource and patients perspective appears to be most beneficial in tumor surgeries (specially pediatric), epileptic surgery and DBS.