The origins of this book lie in Lesley Milroy’s Observing and Analysing Natural Language (OANL) which first appeared in 1987. While the general orientation of that work has been maintained, and some of its material has been reproduced here, the tremendous expansion of the field has necessitatedthat the original work be substantially revised and updated for the current project. A good deal of new material has also been included to treat issues that have since emerged as significant (see, for example, the discussions of instrumental techniques for analyzing phonological variation (section 6.3.2) and the treatment of style-shifting as a strategic maneuver (section 8.3) ). The additional perspective provided by the co-author, Matthew Gordon, serves to distinguish further the current work from OANL. The basic structure of the book partly follows that of OANL. Chapter 1 offers a theoretical introduction to the general framework of variationist sociolinguistics, and is followed in chapters 2 and 3 by a discussion of study design and methods of data collection. Chapters 4 and 5 explore issues related to the social dimensions of language variation, and chapters 6 and 7 focus on linguistic issues, discussing various aspects of data analysis and interpretation related to phonological variation, and grammatical variation. Finally, style-switching and code-switching are examined in chapter 8.