In this paper, we review all of the contributions to TWG18, focusing on the range of research interests, theoretical perspectives and frameworks, and methodological approaches. From this review, the research presentations, and discussions, the following future directions have emerged in relation to teacher education (TE): 1) Establishing and exploring research informed international design principles; 2) summarising relevant theoretical directions; 3) exploring teacher change from an ethical perspective; and 4) scaling up innovative approaches within TE. In relation to professional development (PD), the following future directions have emerged: 1) Exploring the different roles of participants in PD; 2) exploring what makes change difficult and how professional growth best can be supported; and 3) understanding how we can best build on previous research, and each other, in order to develop the field of mathematics PD research.