In this chapter we describe the underlying principles and most common techniques in diffusion tractography. We cover deterministic streamline tractography and several different probabilistic approaches. We aim to provide a conceptual understanding of the different approaches, but where necessary we introduce mathematical concepts for the more advanced reader. We further address issues of interpretation of tractography results, and of designing a tractography study. We hope the chapter covers the major themes and issues in current tractography research and will provide a reference for both users of diffusion tractography and for those researching new methodological techniques. We end with a discussion of the areas that we believe will make the most fruitful advances in tractography research in the coming years. © 2014 Elsevier Inc. All rights reserved.