Ben Brewster’s translations of For Marx and Reading Capital introduced the work of Althusser and his school to an English readership. They remain widely acclaimed for their fidelity to the original, and their rendering of Althusser’s technical vocabulary has been generally adopted – see the Glossary in this volume. Forty-five years ago, however, many texts of Marx, including Capital itself, were available in English only in out-dated translations, and others such as the Grundrisse not at all. The decision has been made for this anniversary edition to replace all quotations using the Penguin editions of Capital and the Grundrisse, and for other writings the Marx and Engels Collected Works. This has required some correlative changes to the translation of the main text, for example the substitution of ‘worker’ for ‘labourer’, and a few minor adjustments have also been made in the interest of maximum clarity. In the case of Volume One of Capital, Althusser and his colleagues quoted throughout the French edition of Le Capital translated by Joseph Roy and revised by Marx himself. In the situation at that time, Ben Brewster opted to translate these quotations from the French; they have now been replaced as per the Penguin translation, but in cases where Marx made changes for the French edition, this has been indicated.1 Finally, in quotations from Marx, emphases in the original have been indicated by underlining, to distinguish them from emphases in italics by Althusser and his co-authors.