This study examined the construct-related validity of an assessment centre (AC) developed by a national distribution company for the selection and development of lower-grade managers. In five locations throughout Britain, 487 individuals were observed on nine dimensions, each of which was measured through six distinct exercises. Multitrait-multimethod analyses conducted to investigate the convergent and discriminant validity of the AC revealed strong exercise (“method”) effects. This finding was corroborated by an exploratory factor analysis showing that AC ratings clustered into factors according to exercises, rather than according to performance dimensions. A series of MANOVAs and chi-squared tests demonstrated that neither the exercise ratings nor the selection decision were biased by sex, ethnicity, or training location, and a logistic regression determined which exercises had most impact on the final decision.