Tumour ablation is clinically applied mainly for non-operable liver tumours, with increasing application to other organ sites like kidney, lung, adrenal gland and bone. Most current devices use radiofrequency (RF) current to heat tumour tissue surrounding the applicator, which is introduced into the tumour under imaging guidance. Tissue temperatures in excess of 100 degrees C are achieved, with cell death due to coagulative necrosis occurring above 50 degrees C. Limitations of current ablation devices include inadequate imaging, limited size of coagulation zone and reduced performance next to large vessels. This paper reviews current interstitial RF and microwave devices, clinical applications and future research directions in the field of high-temperature tumour ablation.