This study was conducted to examine changes in reflective thinking in preservice teachers in relation to length of time in the teacher education program, teaching certification type, and field placement. Information was collected from student teachers (N=13) through both completion of a questionnaire and through analysis of weekly journals using the Pedagogical Language Acquisition and Conceptual Development Taxonomy of Teacher Reflective Thought. It was hypothesized that: (1) preservice teachers would evidence an increase in levels of reflective thinking throughout the field experience, and (2) that preservice teachers placed with university-trained classroom teachers would be more reflective than those placed with other veteran teachers. Data analysis revealed that length of time in the teacher education program and teacher certification type were significantly related to reflective thinking, and that preservice teachers seeking secondary certification were more reflective than their elementary colleagues. Empirical findings identified curriculum structures that may maximize changes in reflective thinking in preservice teachers and assist teacher educators in implementing the principles of reflective practice. (LL)