In this study we try to settle down the principal points for analysing bullying in Spanish Schools (Primary and Secondary Schools), using the same instrument, the Bull-S questionnaire, very well validated and used in different Countries and Contexts. This study presents data from the development of bullying from 1990 to 2006, in Spanish Schools, in terms of level of incidence. Also included the analysis of the personal characteristics of those involved pupils, sociometric aspects, and situational points like, frequency, ways and places where bullying takes place and the self-report of the importance and incidence in security perceived by the whole class-group. All these aspects can contribute to the knowledge of the prevalence and diffusion of bullying.