[영문]Over the past quarter-century, evaluation researchers have recognized the importance of documenting implementation practices of programs as they are transferred from controlled to realworld settings. As programs become widely disseminated in the general population, there is a tendency for practitioners to alter programs in a manner more conducive to their immediate needs, which may adversely affect program outcomes. The current paper uses findings from an ongoing evaluation of a school-based victimization prevention program to highlight some of the difficulties in maintaining a high degree of fidelity when providing prevention programming in a school-based setting. The results, based on observations of program delivery and program provider descriptions of implementation, allow for the examination of fidelity based on different data collection techniques.