The field experience component in the four-year Bachelor of Education programme (Primary) at The Hong Kong Institute of Education offers a number of opportunities for students to observe or teach in a school. The aim of this article is to analyse the learning of the student-teachers and the supporting teachers during the field experience period in the second and the final years of the programme and to explain this learning using a sociocultural view of learning. Student-teachers and their supporting teachers in their second year of study in 1999-2000 as well as those in their final year of study in 2001-02 were interviewed. The findings describe the professional development of the student-teachers and the construction of knowledge in teaching. The article analyses the role of supporting teachers as social agents, and describes their use of mediational means, including teaching resources, and information about pupils' abilities and habits, in facilitating the learning of the student-teachers. The findings also compare the sharing of aims between the lecturers and the supporting teachers. Finally, the paper summarizes suggestions on how professional development of the student-teachers during the field experience may be analysed by adopting a sociocultural view of learning. (Contains 3 figures and 1 note.)