This text provides an introduction to the field of sociolinguistics for second and foreign language teachers. '... like companion volumes in the Cambridge Applied Linguistics series, it is readable without over-simplifying detailed arguments ... One of the aspects I particularly like in this book is the frequent and explicit references to learners and their teachers in specific situations. This ensures accessibility of the information to both the academic and to the classroom teacher, for whom much of the information will be of great use.' VATME Newsletter No 71, 1997