Medical infrared imaging captures the temperature distribution of the human skin and is employed in various medical applications. Often it is useful to cross-reference the resulting thermograms with visual images of the patient, either to see which part of the anatomy is affected by a certain disease or to judge the efficacy of the treatment. In this chapter, we show that image registration techniques can be effectively used to generate an overlay of visual and thermal images and provide a useful diagnostic visualisation for the clinician.