As I indicated in the Preface, this book is not a review of ageing. It will also become apparent to the reader that the level of documentation and citation of previous publications is quite uneven. Sections of the book that deal with general or biomedical topics, such as the pathological changes that often accompany human ageing, are almost absent of references. Much of this information is available in standard medical texts or monographs. In other parts of the book I cite wherever possible previous reviews or collections of publications that cover a particular topic. There are innumerable reviews of different aspects of ageing, including three editions of the Handbook of the Biology of Aging (Van Nostrand Reinhold, 1977, 1985; Academic Press, 1990) and the CRC series on ageing, which comprises at least 12 volumes on diverse topics in gerontology. The sections that are most thoroughly documented with references are those that have over the years been the focus of my own research and interests: those related to cellular ageing, the accuracy of information transfer between macromolecules and the evolution of ageing. Some of this work has been previously reviewed (Holliday 1984c, 1986b). I am well aware of the more limited discussion of equally important topics, such as the accumulation of abnormal proteins in various tissues, or neuroendocrine interactions.