BACKGROUND We analyze trends in bullying victimization prevalence in a representative sample of Spanish adolescent schoolchildren in 2006, 2010, and 2014. METHODS We distinguish between reported bullying, which is assessed via the global question in the Revised Bully/Victim Questionnaire by Olweus, and observed bullying, which is a measure developed from the answers that the adolescents gave to specific items that refer to different types of bullying that have been codified as physical, verbal, and relational bullying. RESULTS For 2006 and 2010/2014, the results show stability in the assessment of reported bullying and an increase in observed bullying, analyzed both globally and within the 3 categories: physical, verbal, and relational. CONCLUSIONS A valid, reliable, and accurate measure to detect cases of bullying is necessary, as is the importance of continuing efforts devoted to raising awareness and the prevention of this phenomenon.