Assessment centres are often defined as ‘a variety of testing techniques designed to allow candidates to demonstrate, under standardised conditions, the skills and abilities most essential for success in a given job’. Assessment centres are much more time consuming to develop and administer, require more people, and as a result cost more than traditional oral interviews. Why, then, has there been such a dramatic increase in their use? The answer is multidimensional. Firstly, the predictive validity and legal defensibility of unstructured oral interviews have been questioned for years. With the recent trend towards job-relevant testing, selection interviews have become more job-related and structured in format. This change has resulted in improved predictive validity, but generally the validity coefﬁcients achieved are still not as high as those achieved with assessment centres.