Do prehistoric stone monuments in Britain and Ireland incorporate deliberate astronomical alignments, and if so, what is their purpose and meaning? This book by Clive Ruggles is the first to approach this topic -- a subject of controversy between astronomers and archaeologists -- from a perspective that incorporates both disciplines.The book is divided into three parts. The first is a detailed account of the megalithic astronomy debates of the 1960s to the 1980s and the lessons -- both interpretative and methodological -- that can be learned from them. The second describes the present state of ideas and evidence concerning prehistoric people's concerns with celestial bodies and events, drawing particularly on work in British and Irish archaeoastronomy in the past fifteen years, including many years of fieldwork by the author. The third section sets new agendas for the future. The book also includes an appendix on field techniques.The author establishes the importance of studies of astronomy in the context of broader questions of cosmology, ideology, and cognition that are of central interest to prehistorians at the end of the twentieth century. It also makes clear that cross-disciplinary perspectives are necessary in tackling an innately interdisciplinary problem.