Radiation therapy (RT) is an integral part of the treatment of adult soft tissue sarcomas (STS). In extremity STS, RT generally increases local control (LC) compared to wide excision alone while the magnitude of benefit depends on the individual risk profile. Neoadjuvant treatment results in less late toxicity paralleled by improved functional outcome but comes along with increased wound complications compared to postoperative radiation. In retroperitoneal sarcoma, neoadjuvant radiation seems to improve LC at least in liposarcomas while its impact in other histologies remains unclear. Postoperative radiation should not be used except in highly selected cases due to clear disadvantages regarding target coverage and side effects. The introduction of modern radiation techniques like intensity-modulated RT and image-guided RT has further improved the therapeutic ratio and is strongly recommended. Alternative boosting techniques like intraoperative RT or brachytherapy might be used to increase efficacy in high-risk patients although their value has not been proven in modern randomized trials.