We interviewed 13 university teachers who research their teaching practices or their students' learning to identify how they understood their development as teachers. We interpreted recurring themes within the data as three ways of conceptualising university teachers' development as teachers. We use a theoretical model to arrange these conceptualisations in a hierarchy based on levels of engagement in teaching development. The most complex conceptualisation sees this development as high-level engagement involving personal research into practice, with much in common with discipline-based research. We discuss our results in relation to potential and substantial changes in the roles and evaluation of academic developers.