It has long been acknowledged that software methods should be tailored if they are to achieve optimum effect. However comparatively little research has been carried out to date on this topic in general, and more notably, on agile methods in particular. This dearth of evidence in the case of agile methods is especially significant in that it is reasonable to expect that such methods would particularly lend themselves to tailoring. In this research, we present a framework based on interviews with 20 senior software development researchers and a review of the extant literature. The framework is comprised of two sets of factors-characteristics of the method, and developer practices-that can improve method tailoring effectiveness. Drawing on the framework, we then interviewed 16 expert XP practitioners to examine the current state and effectiveness of XP tailoring efforts, and to shed light on issues the framework identified as being important. The article concludes with a set of recommendations for research and practice that would advance our understanding of the method tailoring area.