The VITAE project is a four-year research study, commissioned by the Department for Education and Skills (DfES), being conducted in seven local education authorities (LEAs) in England. The project, which seeks to work collaboratively with teachers, aims to identify factors that may affect their work and lives over time and how these factors may, in turn, impact on their teaching and subsequent pupil progress and outcomes. The relationship between the qualitative and quantitative research elements in this longitudinal study of teachers lives requires us to combine interviews with 300 teachers with pupil outcome data, crossing a number of 'boundaries' between these different research traditions. These boundaries are a complex mix of technical requirements and the epistemological and methodological principles and practices that distinguish these two broad schools of research. Our approach to crossing these boundaries has been to develop a mixture of digital recording and computer based qualitative analysis to create teacher profiles which highlight teachers' perceptions of what factors have impacted on their work. These profiles form the basis for the multi-level modelling which will try to account for which factors at levels from the teacher, their class, department and school, and external school influences account for variations in their effectiveness. This longitudinal project therefore, uniquely combines quantitative and qualitative methods of data collection and analysis in order to define notions of teachers' relative and relational effectiveness. By the use of these terms we mean that there is no generalisable or universal definition of 'effective'. Relative effectiveness is concerned with variations in effectiveness between teachers in similar circumstances who teach pupil groups with similar characteristics, and between teachers in different school contexts, career phases and life phases. In other words, can variations in effectiveness be explained by commonalities identified amongst, or between, groups of teachers? Thus far, relationships have been explored between effective teaching as defined by pupil attainment measures and contexts such as career phase, life events, pupils' free school meal (FSM) eligibility, school phase, school leadership/support, classroom composition, amongst others.It is clear from the data that the relative stability/instability of identity (motivation, commitment, job satisfaction, self-efficacy, values) plays a major part in determining the impact of these contexts, and that effectiveness is multi-faceted and, if measured only by attainment outcomes, variable for most teachers. However, it was possible to identify a number of outliers (i.e. those teachers who significantly under- or over-performed against their pupil cohorts). This paper will provide a focus for the reasons for such relative performance and will conclude by suggesting areas of teachers' work and lives on which policy-makers and school leaders need to focus if they are to enhance and sustain effectiveness over a career.