This is an analysis of school tutors' assessments of aspects of "Standard one, professional values and practice" (DfES/TTA 2002) for secondary trainee teachers, together with interview data from a sample of trainee teachers and their school tutors/assessors. The paper examines teachers' interpretations of four sub-categories within this Standard and considers these in terms of three key questions: (1) How is the terminology of the standard being defined and described?; (2) How is the evidence for assessment selected and evaluated?; and (3) What are the interpretative frameworks? While this standard is almost universally welcomed as an important component of teacher education in England, its assessment remains elusive for many teachers and tutors. As a result the standard is highly subject to personal interpretations of professionalism and what this might mean in terms of schools' provision for teacher development in this area. The paper supports the use of a framework of teachers' virtues and personal attributes, professional skills and learning and a set of professional behaviours, which might allow for institutional assessment procedures to take better account of both personal and professional development as well as professional competence. The place of critical reflection on practice is considered as a way of clarifying values and, the paper argues, it should become a central component of this standard. (Contains 2 tables, 5 figures and 2 notes.)