The optimal approach to assessing surgical margins continues to be debated in pediatric surgical oncology. Technologic innovations have motivated the increased use of multidisciplinary intraoperative adjuncts involving radiology and pathology support. Some margin-assessment methods, including intraoperative frozen biopsy and ultrasound image–guided tumor resection, have been extensively analyzed in the literature, but those approaches have limited accuracy and multiple indications. Preliminary reports of recent technologic advances, such as three-dimensional imaging reconstruction and fluorescence-guided surgery, show promise to improve tumor resection in pediatric surgical oncology. In this chapter, we describe the available margin-assessment methods and highlight the potentially improved accuracy of these new technologies.