This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book contributes in various ways to symposia on the assessment of special educational needs at the International Special Education Congress in Cardiff in July 1990. What initiatives will empower children and parents to contribute to assessment and influence its outcome? How best can assessment be undertaken so that it supports integration and mainstreaming? What growth points can be identified in the practice and the technology of assessment that will support those aims? Special educational needs are being defined in new ways. Changing laws and changing perspectives in many countries present new challenges to practitioners. The fundamental shift underlying all these changes is the idea that handicap is not an absolute phenomenon, that special educational needs are relative to a person's environment.