The first part of this book explores the literature on professionalism in general and relates that to the practice of ELT. Professionalism as it is understood by medical practitioners and architects in the UK applies where the service required is so complex and the knowledge involved so wide that clients cannot be relied upon to look after their own interests in choosing the service they require. The professional therefore becomes responsible for defining the service as well as supplying it. The argument of this book is that ELT is every bit as complex and the client just as vulnerable as in medicine and architecture, and that professional system of service and accountability are appropriate and achievable. Whether the cost is too high is another matter and outside the scope of this book, but the benefits may be significant.The merit of the idea professionalism in ELT may be measured by what can be done with it. The second part of this book deals with applications of the principles established here to some of the problems that face ELT practitioners.This book will be of interest to all ELT professionals, both teachers and administrators, who may need to understand the professional context of language education.