This chapter focuses on Infections in Orthopaedic Oncology in those cases when there is no reconstruction after tumor resection, after curettage surgeries, and when the reconstruction after resection is not a prosthetic reconstruction. The rate of Surgical Site Infections (SSI) in Orthopaedics ranges between 0.2% and 4.2%, it is lower in arthroplasties (around 0.2%) and higher in spine surgery (reaching 4.2%). In Orthopaedic Oncology the infection rate is higher than in Traumatology and standard Orthopaedics, due to the different typology of patients, the associated therapies (chemotherapy and radiation therapy), and the often more invasive surgery. While the rate of infection in megaprosthesis is well studied and ranges between 9.3% and 20.4%, depending on the site of the prosthetic reconstruction, the infections in other types of Orthopaedic Oncology surgeries have been described in the scientific literature, but with a less homogeneous approach compared to the megaprosthesis, and usually presented not as a standing alone topic but together with outcomes and other complications. The analysis of infection risk in Orthopaedic Oncology shows a higher patient-specific risk of SSI in case of malignancy, smoking history, and a higher American Society of Anesthesiologists (ASA) score. While procedure-specific risk factors for SSI are considered surgical time, blood loss, blood transfusion volume, neoadjuvant chemotherapy, neoadjuvant radiation therapy, inpatient type of surgery, and number of previous surgeries on the same site. These last two factors are highlighted to be independent predictors of SSI.