In the "what works" agenda, the case for replication studies in education has strong proponents and supporting arguments. This paper outlines some of their key claims and argues that replication studies, whilst potentially making an important contribution to the "what works" and evidence-based agenda, and education more widely, face several challenges in the context-dense, variable-rich field of education. The paper indicates key challenges facing replication studies in education, from definitions to conception, conduct, interpreting, and drawing conclusions from findings. It sets out how replication studies in education might be improved and developed, and how to address challenges. What replications bring to education is important and useful, but exacting, and, like other research in education, they are not straightforward. Changes of mind-set of researchers, publishers, and funders are needed in order to enable replication studies to prosper, together with attention to what constitutes valid and reliable replication.