This chapter explores the key principles underlying open surgical procedures in pediatric oncology. It traces the historical evolution of cancer surgery, from the radical techniques of the early twentieth century to the more conservative approaches of today. The chapter emphasizes the distinctions with minimally invasive surgery, with which it is frequently compared. The chapter tries to provide broadly applicable principles that can be followed regardless of tumor type and anatomical region with commonly encountered practical examples. Key concepts such as tumor resectability, surgical access, dissection, resection, and reconstruction as well as recovery are discussed. Through this detailed exploration of the 7R principles, the chapter serves as a comprehensive guide for oncologic surgeons to optimize outcomes in pediatric cancer surgery. Through this detailed exploration of the 7R principles, the chapter serves as a comprehensive guide for oncologic surgeons to perform open surgery and understand its place in the armamentarium of pediatric cancer surgery.