Within the euHeart project, WP6 aims at developing personalized biophysical models of the atria and ventricles in order to improve the planning of radiofrequency ablation (RFA) on patients suffering from atrial fibrillation (AF) and ventricular tachycardia (VT). Besides the collection of patient specific data, one important task to achieve the goals of this workpackage is to define the biophysical models on which will be the personalized simulation of AF and VT. For the atria, the Courtemanche-Ramirez-Nattel (CRN) model is used by IBT to model atrial electrophysiology whereas for the ventricles, INRIA has adopted the Mitchell-Schaeffer (MS) model to capture in a simplified way the main features of the ventricles depolarization and repolarization. In both cases, fast versions of these electrophysiological models are proposed to decrease the time of computation on patient specific models having a large number of elements. Furthermore, those models of cardiac electrophysiology take into account the fast anisotropic pathways (myocardial fibers, Bachmann bundle...) that are anatomically defined in the atria and ventricles. The simulation of the ventricle electrophysiology is coupled with a myocardium mechanical model which simulates the myocardium deformation, chamber volume and pressure during a cardiac cycle. To simulate the pathological wave propagation involved in AF and VT, specific parameters and initial conditions of those electrophysiology models are defined reflecting the effect of atrial remodeling or scars. Some simulations of AF and VT are provided on simplified geometries as well as realistic patient specific meshes. Finally, a workflow for the evaluation of those AF and VT models is provided involving the following stages : image acquisition, image processing, personalization of the geometric and biophysical models, RF ablation lines planning.