This study tested 51 characteristics of bullying victimization, bullying victims, and bullying victims' schools to determine which were associated with reporting to school officials. It found that 11 characteristics in two categories--bullying victimization and bullying victims--showed a statistically significant association with reporting. The study also notes the high percentage (64 percent) of respondents who experienced bullying but did not report it. Eleven characteristics were found to have a statistically significant association with reporting of bullying victimization, specifically: (1) Eight characteristics of bullying victimization were statistically associated with increased reporting: bullying involving injury, physical threats, destruction of property, actual physical contact (pushing, shoving, and the like), greater frequency, multiple types, more than one location, and at least one occurrence on a school bus. Seven characteristics did not appear to be associated with reporting: bullying that involved making fun of the victim or calling the victim names, excluding the victim, spreading rumors about the victim, and forcing the victim to do things he or she did not want to do, and bullying that occurred in the school building, on school grounds, or somewhere else. (2) Three characteristics of bullying victims were found to have statistically significant relationships with reporting. Grade level was significantly and negatively associated with reporting, and being involved in a fight during the school year and being afraid of attack and avoiding certain school areas or activities were significantly and positively associated with reporting. Victim characteristics that did not appear to be associated with reporting included gender, race/ethnicity, household region, and academic performance. (3) No characteristic of bullying victims' schools--including general characteristics, school culture, and school security and safety--was found to have a statistically significant association with reporting. The results should be interpreted as exploratory associations between the reporting of bullying and various student and school characteristics and not as confirmations of causal relationships. Appended to this report are: (1) Previous Research on Bullying; and (2) Data Source and Methodology. (Contains 15 tables, 2 figures, 1 box, and 7 notes.