Literature about clinical prediction rules (CPRs) is growing exponentially, and it's one of the hottest topics in physical therapy today. Fundamental differences of opinion exist regarding the optimal approach to identifying whether subgroups of more homogeneous patients respond to a specific type of intervention. What’s the current state of CPR development—and what does it all mean for practice and research? When it comes to day-to-day clinical decisions, how confident can you be about these data? In July 2009, PTJ published a Perspective titled "A Guide to Interpretation of Studies Investigating Subgroups of Responders to Physical Therapy Interventions" by Mark Hancock, Robert D. Herbert, and Christopher G. Maher. In this podcast, 2 of the authors debate the issues with Julie Fritz. As Fritz notes, “a big problem we all deal with is the amount of variability that there is in practice.” This podcast debate faces the hard questions head on.