This handbook has been compiled to provide a reference for teachers at all levels who are implementing the metric system in their classroom. It includes practical suggestions and recommendations for teaching the metric system, as well as papers identifying and discussing the fundamental mathematical and psychological issues underlying the teaching of the metric system in the schools. The articles--some reprinted from recent issues of the "Arithmetic Teacher," some written especially for this publication--are organized under five headings: Introducing the Metric System; Teaching the Metric System: Activities; Teaching the Metric System: Guidelines; Looking at the Measurement Process; and Metrication, Measure, and Mathematics. (Editor/DT)