Several approaches to response to intervention (RTI) described in the literature could be blended into an RTI model that would be effective in the schools. An effective RTI model should employ three fundamental variables: (a) systematic data collection to identify students in need, (b) effective implementation of interventions for adequate durations, and (c) review of student progress data to determine when and/or if more intensive services are warranted. Research regarding RTI elements such as intervention time, intervention duration, treatment efficacy, intervention group size, measurement of student progress, and decision analyses is reviewed. Recommendations for future research include further defining the element of intervention time with regard to frequency and duration, determining the effect of the individual delivering the intervention, and specifying a reliable decision-making rule for determining student responsiveness/nonresponsiveness to interventions.