Reliable and accurate information regarding the heat distribution inside biologica.I tissue due to microwave thennal ablation is essential for the design and optimization of safe therapeutic applicators and for the development of experiments, which aim to investigate their effects. To date, very few finite element models (FEM) have been developed to describe and illustrate electric field penetration, specific absorption rate (SAR) and temperature distribution in biological tissue due to microwave ablation probes. A coupled field finite elemerit analysis model that accounts for the temperature dependent conductivity and blood perfusion changes has not, as yet, been developed for ablation type devices. Although it is widely acknowledged that accounting for temperature dependent phenomena may affect the outcome ofthese models, the effect has not yet been assessed for microwave tumour ablation (MTA). This thesis aims to develop an improved non-linear coupled field electromagnetic and thermal FE model of microwave ablation, incorporating temperature dependent electrical and thermal properties of, ex-vivo bovine liver. Measurements of temperature dependent ex-vivo bovine liver electrical permittivity are made and their effect. presented. Temperature dependent thennal properties of the tissue are limited. to temperatures below phase change. Therefore, a theoretical tissue model for going changes in phase is also presented. The FE model of microwave ablation is based on a 2.45 GHz minimally invasive dielectric loaded monopole antenna