This study investigated two questions: a) What is the relationship between reflection and professional development? and b) What is the role of reflection in teachers' instructional decision-making? Teachers are often conflicted by competing theories (e.g. behaviorist vs. constructivist) and principles (progressives vs. essentialists) at both national and state levels. Other sources of conflict teachers encounter stem from standards-based teaching, student assessments and teacher evaluations. For over eighty years educational theorists (e.g., Dewey, 1933; Fenstermacher, 1994; Schon, 1983) have suggested that reflection is an important key for resolving conflict and improving curriculum and instruction. Yet, top-down professional development models currently prevail rather than creative, individualized models that are designed to encourage reflective thinking and support teacher growth. Research has suggested that although reflection is necessary, reflective thinking can be challenging for teachers. For example, the Reading Instruction Study (RIS) (Richardson & Anders, 1994), which this study is patterned after, found that teachers who examine and link theory to their practice were more likely to change when their beliefs were challenged. In addition, other researchers (e. g., Wildman & Niles; 1987; Wlodarsky & Walters, 2006; Woolley & Woolley, 1999) have suggested that there are differences in reflection among more experienced teachers versus novice teachers. This study considers differences in reflective thinking. This instrumental case study (Stake, 1995) examined the reflective thinking of four teachers (two 3rd grade and two 6th grade) using practical argument (Fenstermacher, 1994) as a tool for analyzing their practices. Belief statements served to bridge theory and practice encouraging teachers to be more coherent in their classroom decision-making and instructional practices. The professional development sessions offered throughout this process provided opportunities for teachers to reflect. Results revealed that participants' reflected in and on practice in different ways that seemed to bring about a change. Not only did articulating beliefs provide opportunities for teachers to examine and link theory to practice, practical arguments provided a means for examining inconsistencies between beliefs and practice, differences in reflective language, and the dimensions of reflective thinking used by teachers with varying degrees of experience. Findings further suggest that when challenged, beliefs change. The language revealed in participants' reflections varied between every day and academic depending upon their dimension of reflective thinking. Language mattered. Not only was movement between personal and public theories impeded by a lack of academic language, movement throughout the five dimensions of reflective (Griffiths & Tann,1992) thinking was likewise hindered by a lack of academic language. Implications are provided for teacher education, professional development and further research. Conclusions call for educators and policy makers to recognize the complexities of teaching, the importance of reflection in coping with conflict, and the need for change in prevailing professional development models.