Based on the International Commission on Mathematical Instruction conference held in early 1987, this volume consists of a number of key papers presented by international authorities on the role of mathematics in applied subjects, such as engineering, computer science, and mathematical modelling. The importance of certain mathematical ideas, such as geometry and discrete mathematics is stressed, as well as the more classical methods. The book includes a long article by the editor synthesising some of the main themes and trends debated at the conference.