The ancient burial sites of Knowth, Newgrange and Dowth make up the archaeological complex at Brugh na Boinne, a UNESCO world heritage site which has attracted enormous international interest. George Eogan began excavating the site at Knowth in 1962 and this is the sixth volume of the Excavations at Knowth monograph series. Volume 6 aims at reconstructing the archaeological history of the achievements of the passage tomb builders who created and utilised the great mound (Tomb 1) at Knowth over a period of at least three centuries, c. 3200-2900 BC. It is hoped that the research presented in this volume will lead to a better understanding of the people who built the passage tomb cemetery at Knowth, and also contribute to the wider appreciation of society at the time of its construction and use.