Mindfulness-Based Stress Reduction (MBSR) courses are being taught around the world in various contexts and targeted to various populations. The program has been intentionally designed without a detailed teaching manual so as to allow instructors to respond to what is called for in each teaching moment. It also affords tailoring the program to specific circumstances such as when working with persons suffering from depression or substance abuse. But how does one remain true to core teaching intentions and program components, while undertaking such tailoring? Modifications to the format and content of MBSR have been reported but little is known if these adaptations influence outcomes and processes underlying change compared to the basic curriculum. Here we discuss what we consider to be essential aspects of the program to be carefully considered when adapting it. We describe selected adaptations of MBSR to highlight the types of changes made and report results when data are available. We conclude with suggestions pertaining to how to best remain authentic while being imaginative regarding the administration of MBSR in non-medical settings (e.g., prison) and for special populations (e.g., women with addictions).