This study examined how participants in the Masters in Secondary Education with a Middle Level Emphasis Program (MLMED) at the University of Hawaii perceived their personal experiences with the portfolio process in shaping their middle level teacher preparation and professional practices. The process involved understanding a standards-based teacher portfolio, generating evidence or artifacts, discussing artifacts, sharing portfolio progress, generating reflective writing, defending the portfolio, and using the portfolio following program completion. The study used qualitative case methods that focused on the portfolio process for all 62 participants in the first two cohorts of MLMED. Participants completed electronic open-ended questionnaires, focus groups, and individual interviews. The study shows that the MLMED portfolio process promoted a deep understanding of the professional standards of middle level educators and teacher motivation to see themselves as effective agents in the larger picture of the school systems in which they work. The MLMED portfolio, as part of a process that includes sustained collegial support, leads to perceptions of improved professional practice and serves as an effective professional development model. (Contains 33 references.) (Author/SLD)