This book discusses the implications of new informationtechnologies and cognitive psychology for mathematicalproblem solving research and practice. Based on a NATOAdvanced Research Workshop held in Portugal in 1991, itoffers both empirical research and theoretical papers. The book includes a thorough discussion on the nature andpurpose of problem solving as a mathematical activity,providing a view of the importance of complementaryactivities such as investigations, conjecturing and problemposing. It focuses on cognitive processes, instruction,classroom processes, and the teacher's role, and containsnew assessment and teacher education proposals. At a time of important reform movements, when emphasis isput on the role of new information technologies, the bookprovides an up-to-date view of the developmental work beingdone on computerized learning environments in the disciplineof mathematics, as well as on the efforts to introduce themin educational practice.