This chapter presents a review of the numerical tools and experimental methods that can be used to model and assesses the interaction of mobile communication devices with the human body. Analytical methods can be applied to simplified canonical geometries modeling the human body. Analytical methods are restricted to very simple configurations, but they provide valuable insight into the physical mechanisms, yield typical parameters, and they are used for testing of numerical methods. The numerical methods used to evaluate the power absorption into biological bodies mainly include the method of moments, the finite difference time domain method, the finite integration technique and the finite elements method. Since in numerical methods the device must be replaced by a numerical model, a significant error can be produced. To provide realism for experimental modeling, several investigators have developed realistically shaped, heterogeneous models that are filled with several different tissue-simulant liquids/gels to represent specific parts of the human body.