This paper reports on the effects of a graduate course on teaching and learning on graduate teaching assistants' conceptions of teaching and on the teaching philosophy statements that arose from those conceptions. Effects are interpreted from three perspectives: 1) course facilitators' reports of their perceptions of course participants' conceptual change; 2) an independent assessors' ratings of the evidence of change through blind review of course participants' initial philosophy statements and final statements; and 3) participants' own perceptions of change and identification of the course components and learning activities that were most significant in their conceptual development. Findings suggest that graduate teaching assistants' perceptions of conceptual change differ significantly from those of both the course facilitators and the independent assessor.