Examined preservice teachers' epistemology (sources of pedagogical knowledge and orientation to knowing) in relation to teaching problem readers and the influences of participation in a reading diagnosis course on their epistemology. Ss were 122 undergraduate students enrolled in a compulsory reading diagnosis course over 2 semesters; Ss individually analyzed problem reader case studies prior to and following the course. Analysis of 6,280 statements from 244 case studies indicated 3 epistemological orientations: received, subjective, and procedural ways of knowing. The course experience was found to impact the relationships between different sources of pedagogical knowledge, urging the Ss toward greater objectivity in their pedagogical thinking. Postcourse responses were more balanced between subjective and procedural orientations.