Education is key to the implementation of commitments made at the recent United Nations World Summit on Sustainable Development (WSSD) in Johannesburg. The Implementation Plan demands communication of the issues ond engagement of people in action and informed decision-making for an improved environment. It positions education as a critical tool for social change and places high expectations upon education and more specifically upon formal environmental education. However, there are concerns that prospective and practising teachers are not up to the challenge. This paper reports the results of two independent studies, namely a qualitative ethnographic study and a quantitative survey, which investigated final year primary education student teachers' pedagogical content knowledge of environmental education. Both studies revealed that student teachers possess limited knowledge of environmental education content and pedagogy. The student teachers tended to dismiss the importance ofsubstantive knowledge, preferring to focus upon the formation of attitudes towards the environment. Thus, the results of this study suggest that Australian primary schools will struggle to meet the outcomes agreed upon at the World Summit for Sustainable Development. These findings have significant implications for environmental education and, in particular, for the commitments made at Johannesburg. A lack of teacher education in environmental education may explain why primary schools are not meeting policy expectations in this area of learning. However, this study suggests that a renewed focus upon knowledge, specifically pedagogical content knowledge, is timely and necessary in environmental education if the field is to evolve.