The First Stones brings together the results of recent research on the Neolithic long cairns lying in the shadow of the Black Mountains in south-east Wales, focusing upon Penywyrlod and Gwernvale, the two best known tombs within the group, previously excavated in the 1970s. Important results lie in both new site detail and reassessment of the wider context. Small-scale excavation, geophysical survey and geological assessment at Penywyrlod – the largest of the Welsh long cairns – gave further information about the distinctive external and internal architecture of the monument. In turn, this opened the opportunity to reassess the pre-monument sequence at Gwernvale, with re-examination of both Mesolithic and Neolithic occupations, including a timber structure and midden, lithic and pottery assemblages, and cereal remains. The frame for wider reassessment is given by fresh chronological modelling both of the monuments themselves, suggesting a sequence from Penywyrlod and Pipton to Ty Isaf and Gwernvale, probably spanning the 38th to the 36th or 35th centuries cal BC, and of early Neolithic activity in south Wales and the Marches, probably beginning in the 39th century cal BC. A detailed study of the major assemblages of human remains from the Black Mountains tombs includes evidence for diet, trauma and lifestyles of the populations represented. Recent isotope analysis of human remains from the tombs is also reviewed, implying social mobility and migration within local populations during the early Neolithic. The First Stones makes a significant contribution to the study of tomb building, treatment of the dead, place making, the relationship of monuments to landscape, local and regional identities, connections and affiliations across southern Britain and the adjacent continent, and Neolithisation in western Britain. Viewed within the context of tombs within the Cotswold-Severn tradition as a whole, it leads to an appreciation of the local and regional distinctiveness of architecture and mortuary practice exhibited by the tombs in this area of south-east Wales, emerging as part of the intake of a significant inland area in the early centuries of the Neolithic.