This Dartmouth Atlas of Health Care reports on unwarranted regional variation in the care of several conditions for which surgery is one important treatment option. Unwarranted variation is the differences in care that are not explained by patient needs or preferences. Each chapter begins with an examination of the underlying condition, the available treatment options before surgery, and the role of shared decision-making. The care during surgery is then presented, including aspects of quality, risks, and costs. The next section is concerned with the care of patients after surgery, including hospital readmissions and ambulatory care.