Project VIABLE: Validation of Instruments for Assessing Behavior Longitudinally and Efficiently An extensive knowledge base exists with regard to establishing a full continuum of PBS practices that can support all youth (Center on Positive Behavioral Interventions and Supports; Gresham, Sugai, & Horner, 2001; Sugai & Horner, 2005), however, the technology for formative evaluation of individual and specific behavioral response to those practices has not kept pace. The importance of progress monitoring, particularly for students exhibiting serious behavior problems, cannot be overstated. Yet, a significant gap exists regarding available tools for behavioral progress monitoring that are empirically-supported and, equally important, feasible for use in applied settings. Empirical attention to the development and validation of viable formative measures of social behavior is essential if we are to effectively evaluate the success of positive behavior interventions put in place to address challenging student behavior.