Over the past 25 years, image-guided thermal ablation has emerged from basic science investigations to clinical practice and is now an established technique for treatment of patients with a variety of soft tissue tumors, including primary or metastatic liver cancer, kidney cancer, breast cancer, thyroid tumors, and benign and malignant bone tumors. Image-guided thermal and nonthermal ablation techniques and the list of tumors that can be treated by ablation continue to expand. Benefits of thermal ablation include less morbidity, shorter recovery, and comparable short- and long-term clinical outcomes when compared to more invasive options. Indeed, several professional societies now include ablation techniques within their guidelines treatment options. This chapter will review currently available ablation devices with a focus on their mechanism of action and application.