When a person embarks upon a professional scientific career, what features define their training process? How is this process related to scientific practice and, in general, its development within the organisational setting of the R&D system? The changes affecting contemporary science since the late 20th century mirror several characteristic features of the scientific profession, namely the working conditions of scientists, how professional careers are organised, the way in which scientific work is assessed and how scientists are trained in the academic world. Researchers in academic science today are faced with far-reaching reforms which are currently taking place in universities and official research centres; changes which respond to the growing complexity in the organisation of scientific work and the pressures of science and university policy. Insofar as traditional researchers were considered academic workers, scientists in the public sector must now satisfy the organisational requirements of disciplines and institutions alike. This changing situation has affected the way in which new scientists are recruited and trained and the rôle played by both the doctoral thesis and the young researcher in scientific groups. These changes have also had repercussions for new researchers in their process of socialisation , deepening the trends of social change in academic science, especially in those institutions and R&D systems that are more firmly anchored in the traditional organisational patterns of academia. This paper examines the significance of these issues and illustrates empirically how young researchers are trained in Spanish academic institutions. Through surveys of grant recipients and researchers, discussion groups and in-depth interviews, the training strategies carried out in a range of scientific disciplines and the organisational contexts of Spanish science are examined along with the specific ramifications this situation has for the social restructuring of science in Spain.