Six of the eleven papers in this volume are revised versions of those given at a symposium session at the SAA meeting in Chicago in 1999, along with an introduction and four extra contributions. The papers discuss object, behavioural and process replication and include both specific case studies, such as `Controlled experiments with Middle Palaeolithic spear points', to more general studies of `Assessing the process of experimentation'.Six of the eleven papers in this volume are revised versions of those given at a symposium session at the SAA meeting in Chicago in 1999, along with an introduction and four extra contributions.