The key aim of the present research was to study the “functionality” of two global variables in the Olweus Bully/Victim Questionnaire and to examine the appropriateness of different cutoff points of these variables for prevalence estimation. Several empirical and conceptual analyses strongly attested to the functionality of the two selected variables in terms of construct validity and selected measurement properties. Similarly, a number of analyses indicated that (having been bullied/having bullied other students) “2 or 3 times a month” was a reasonable and useful lower-bound cutoff point. With this cutoff point, “involved” students, victims, and bullies differed very markedly and in clearly different ways from “non-involved” students in conceptually related variables. Prevalence estimates derived in this way can be conveniently obtained, have a reasonably well-defined meaning, can be easily understood by users, and can be reproduced unambiguously by different researchers/administrators and at different times. An important background for the article is the fact that several common methods, including peer nominations, are not well suited for prevalence estimation. Prevalence data for victims, bullies, and bully-victims are also presented. All data were derived from the New Bergen Project Against Bullying, comprising a sample of 5,171 students from 37 schools in the town community of Bergen, Norway. At the time of the data collection, the spring of 1997, the 2,544 girls and 2,627 boys were in grades 5 through 9, with modal ages of 11 through 15 years. Aggr. Behav. 29:239–268, 2003. © 2003 Wiley-Liss, Inc.