Nurses are now directed to 'reflect effectively and practice reflectively'. When there is scant evidence to support the use of reflection, why does the United Kingdom Central Council, English National Board for Nursing Midwifery and Health Visiting and institutes of nurse education insist that nurses, at all levels of experience, reflect? Before developing the debate in relation to the robustness or otherwise of the concept of 'reflection' and its application to practice, a discussion as to what constitutes nursing knowledge, followed by an examination of the main theories related to adult learning, is presented. The paper develops to encompass a critical examination of both theoretical and applied perspectives on reflection. Conceptual issues and assumptions related to reflection are explored. Key areas considered are whether the practice of reflection facilitates the improvement of one's knowledge, helps to generate theory and results in one becoming a more critical practitioner with resulting benefits for patients. It will be argued that reflective theory and practice has not yet been adequately tested and that there is a pressing need for evidence to demonstrate irrefutably the effectiveness of reflection on nursing practice, particularly with respect to patient outcomes.