ABSTRACT At a time when the focus of school science policies in many nations is to encourage more pupils to study science for longer, a better understanding of who is and is not interested in STEM careers will play an important role in shaping the guidance that schools can provide their pupils and the interventions that seek to inspire more young people to remain in the science stream. This paper explores the career aspirations of more than 4000 pupils at the end of lower secondary school in the UK. It considers the relationship between career aspirations, pupil characteristics, and school-based factors linked to enjoyment of and motivation for learning about science. The findings show that most pupils enjoy and look forward to studying science and feel that they are successful at it whether they aspired to a career in STEM or not. The study also confirmed the multi-dimensional nature of STEM career aspirations in which underlying inequalities, particularly linked to gender and ethnicity, were very much apparent. The complexity of these relationships confirms what decades of initiatives have told us – that increasing the number of young people who study science and later enter the highly skilled STEM labour market is no easy task.