District implementation of the response to intervention (RTI) model has occurred at a surprising rate. It appears that implementation of RTI has occurred rapidly and is being implemented with all students. Rapid implementation of RTI is occurring alongside continued controversy over the model and its intended uses. Although significant research support exists for the components of RTI, the question remains about the loss of fidelity and inconsistency in implementation when these components are scaled up (i.e., the process of expanding the implementation of RTI with fidelity across classrooms, grade levels, schools, districts, and states). Some research has addressed this issue, but little research on the relationship between the process of implementation and outcomes has been published. The development of the program evaluation model for the Florida Statewide Problem-Solving/RtI (PS/RTI) initiative is intended to examine the factors that influence fidelity in the scale-up process. The model was designed to evaluate the relationships between teacher variables (e.g., beliefs), response to professional development (e.g., skill development), implementation levels of PS/RTI, and student outcomes. Reviewing the data predicting the outcomes of these relationships should make the process of scaling up both effective and efficient. (Contains 1 figure and 2 tables.)