The use of the cognitive interviewing method for survey question testing has proliferated and evolved over the past 30 years. In more recent years the method has been applied to the evaluation of information letters and leaflets and to research consent forms. This book provides a practical handbook for implementing cognitive interviewing methods in the context of applied social policy research, based on the approach used by the authors at the NatCen Social Research (NatCen) where cognitive interviewing methods have been used for well over a decade. The book provides a justification for the importance of question testing and evaluation and discusses the position of cognitive interviewing in relation to other questionnaire development and evaluation techniques. Throughout the book, the focus is on providing practical and hands-on guidance around elements such as sampling and recruitment, designing probes, interviewing skills, data management and analysis and how to interpret the findings and use them to improve survey questions and other documents. The book also covers cognitive interviewing in different survey modes, in cross national, cross cultural and multilingual settings and discusses some other potential uses of the method.