Along with discussion of format and design of electronic portfolios, this article addresses the larger question of what happens to teachers when they invest in creating a professional portfolio. Are they able to transform this experience into more authentic assessment with their own students? Beside acquiring proficiency in using portfolio development tools, do teachers find that their core beliefs and philosophies related to these tools been altered? Seventy-eight teachers created e-portfolios during their participation in a graduate-level education course. Quantitative and qualitative data were collected and are explained in terms of Mezirow's transformational learning theory. While not all of the teachers seemed ready to replicate the process of developing electronic portfolios with their students, it is clear that they were transformed by the process of creating their own. In particular, the content addressed through this particular portfolio and the format of the course (collaboration, critical reflection, supportive discussion, and individual construction of learning experiences) did facilitate transformative learning. (Contains 1 table.)