There has been a longstanding consensus that both pre- and in-service teachers need more content knowledge. Shulman’s (1986) differentiated between three forms of content knowledge: subject matter knowledge, pedagogical content knowledge and curricular knowledge. This symposium reports on the results of series of studies conducted over the past four years focused on the subject matter knowledge pre-service teachers have acquired prior to entering their teacher education program, and the content knowledge that they acquired during their program. The presenters' focus is on the question: What do teachers need to know about their subject matter in order to teach it?