Teachers' conceptions of teaching, including assessment practices, are substantial in directing student learning. Our article refers to assessment at tertiary level biological education. We studied life science (more specifically microbiology-related) teachers' assessment discourse describing how they understood assessment as part of their teaching, how they justified their assessment practices, and how they saw their own as well as the students' role in the assessment processes. We identified three categories of teachers' assessment discourse based on the level of reflection and pedagogical awareness, action and partnership. Within each category, we present characteristic features found in three themes: assessment practices, student learning and purpose of assessment. But awareness of the teachers' different conceptions of assessment is valuable from an educational point of view. We suggest that pedagogical education, peer and institutional support, as well as interaction with the wider higher education community, all play an influential role in the development of assessment practices. Our results indicate that assessment practices at the course level must be carefully considered before changing the focus on assessment "for" learning instead of assessment of learning.