This study examined the types of knowledge influencing classroom teaching in higher education. A total of 102 professors from across North America regarded as exemplary teachers participated in the study. Respondents were asked to recall a time during the last 3 years when they thought that they had done a poor job of teaching as well as a time when they felt that they had done an exemplary job of teaching. Respondents were then asked to indicate what types of knowledge had influenced their teaching at each time. The results indicated that four types of knowledge influenced classroom teaching: content knowledge, pedagogical content knowledge, current knowledge of learners, and knowledge of learners' background and appropriate pedagogy. Types of knowledge found not to have a significant impact on classroom teaching included knowledge of curriculum and knowledge of teaching routines. The results were used to develop a model of the knowledge base for teaching in higher education. The findings of the study support the claims that university professors base their teaching, to a large extent, on their knowledge of content. (Contains 32 references.) (MDM)