The Standard Model of the electromagnetic and weak interactions offers no explanations for the origin of the fermion mass and mixing parameters, except that they arise from Yukawa couplings, which are free parameters of the Model. The problem is worse when the question of neutrino masses is considered and, despite its remarkable success on many fronts, the Standard Model cannot explain some important experimental observations. In particular, it is not possible to describe the phenomena of neutrino oscillations that has been uncovered in recent years and, from a particle physics viewpoint, this provides the most convincing evidence for physics beyond the Standard Model. Following the trend of the previous workshops, we focus also on the presentation of the current status of the main accelerator and non-accelerator neutrino mass experiments (such as Super-Kamiokande, and SNO), the future experimental projects (e.g., MiniBoone) and some of the phenomenology related to them, as well as reviews of the theoretical and phenomenological ideas related to the question of neutrino masses and related topics such as the explanation for the observed baryon asymmetry in the universe.