With higher rates of sarcoma patients eligible for curative treatment and increasing survival times, surveillance has become highly important. The goal of surveillance imaging is to detect potential recurrences early and enable timely treatment. Knowledge of typical post-therapeutic changes and their temporal evolution, as well as therapy-related complications, is crucial to distinguish them from recurrence. Proposed surveillance intervals differ between high- and low-grade sarcomas. X-ray imaging and, in complex anatomical regions, CT serve to assess changes in mineralized matrix, while MRI enables the evaluation of bone marrow and soft-tissue changes. PET/CT, commonly using the tracer 18F-FDG, can be helpful in metabolically active tumours. Different from primary imaging, metal artefact suppression techniques are crucial for the assessment of alterations near metallic implants. Adherence to standards for imaging techniques and radiological reporting is essential. Recurrence rates of major sarcoma entities—such as osteosarcoma, Ewing sarcoma, chondrosarcoma, and chordoma—vary and depend on factors including resection margins and the presence of metastases. As an example of non-sarcomatous recurrence, GCT is included in this chapter. The morphology of recurrent lesions on imaging is often characteristic, helping radiologists differentiate them from postoperative changes and complications.