This book describes the programming language Modula-2. It is written for people who know the Pascal language and who wish to learn Modula-2 in terms of their knowledge of Pascal. The text is divided into three parts. Part 1 introduces concepts unique to Modula-2 and thus new to Pascal programmers. Part 2 describes differences from Pascal. Part 3 defines modules which provide basic programming facilities. The appendices include a glossary and syntax diagrams. Please note that this book does not offer a complete description of the Modula-2 language, it is intended to complement Niklaus Wirth's definitive book Programming in Modula-2 (Springer-Verlag, 1983). Some readers will recognize this book as being based upon the Volition Systems Modula-2 User's Manual. Enough has changed to merit its reappearance in this more dignified form: existing material has been reorganized to improve clarity, new material has been added to improve content. This book was written with the ASE text editor. The text was produced in camera-ready form on the Scenic LaserTezt composition system. I wish to thank the following people and organizations for their contributions to the development of this book: Volition Systems, for giving me the opportunity to write about Modula-2, Jim Merritt, for reviewing an early draft, the Institut far Informatik, ETH Zarich, for publishing a series of informative technical papers on Modula-2, and finally, all the pioneer users of Volition Systems Modula-2, for their patience and foresight and support.