Radiofrequency ablation (RFA) is currently the most established technique for the local destruction of tumors within the liver. It is technically straightforward, can be repeated and combines a high efficiency in tissue destruction with a low to moderate incidence of complications. This review explains the principle of RFA and lists currently available systems. In addition, the rationale behind RFA is discussed, and an overview of clinical indications, results and complications is presented. One of the main problems in assessing the clinical value of RFA is the fact that no large and controlled randomized studies are available, while the number of ablations and treated tumor entities are steadily increasing. From a technical point of view, the major problem is the still limited volume of necrosis that is achievable. The indication for RFA has to be discussed as interdisciplinary. A complete tumor necrosis should be the aim of all ablations, with the exception of symptomatic metastases of neuroendocrine tumors. The value of additional chemotherapy to RFA is still unclear, especially in the treatment of liver metastases.