This case study aims to investigate the role of teachers' personal practical knowledge in interactive decision making for three pre-service non-native ESL teachers. The research question is: What role does pre-service ESL teachers' personal practical knowledge (operationalized as teaching maxims in this study) play in their interactive decisions (decisions made "during" teaching)? Content analysis on language learning/teaching autobiographies was carried out to map out teachers' personal practical knowledge. Interviews, observation over time, and a video-based method of eliciting introspective data were employed. The teachers' lesson plans and journals were triangulated with the other data. Findings were that some parts of a teacher's personal practical knowledge might be competitive or conditional while being applied in particular instructional contexts and that while some new maxims start shaping during classroom teaching, some old ones are seen in a new light. Results also show that during classroom teaching, the participants have limited access to their personal practical knowledge (only about half of the interactive decisions made were guided by their personal practical knowledge). However, this played a part in informing post-active decisions (decisions made "after" teaching), and delayed accessibility to such knowledge nonetheless helped evaluate new maxims of teaching. (Contains 2 notes and 7 tables.)