Purpose: This paper aims to describe a qualitative study of a four-year, state-wide portfolio evaluation system for new principals. The State of Ohio (USA) was one of five states that participated in a field test of the Portfolio Assessment for School Leaders designed by the Interstate School Leaders Licensure Consortium (ISLLC) and the Educational Testing Service (ETS). Design/methodology/approach: The central research question was: Does the Portfolio Assessment for School Leaders process benefit or burden the practice of school leaders? The participants were a subset of the 70 principals who completed the portfolio in Ohio between September 1999 and January 2002. The data included focus group interviews, phone interviews, surveys, and the principals' completed portfolios. Findings: From analysis of the data three levels of benefits from level 1 are described, where the portfolio was seen primarily as extra work and had little benefit for the leadership in the principals' schools, to level 3, where there was a reciprocal benefit between the portfolio process and the principals' growth and developed as leaders. Research limitations/implications: This study was limited to one state in the USA, a particular portfolio system, and data were collected from only a subset of principals who completed their portfolios (26 out of 70). Practical implications: The results of this research indicated that the portfolio work was seen as professional development by principals only if it was contextualized in a larger supportive social network of professional practice. It was the use of the portfolio to promote professional development that allowed the portfolio to be a learning tool, and not just a tool of policy compliance. Originality/value: This research adds to the literature on professional development for principals by providing evidence that portfolios can be used with novice principals to support their development as leaders in their schools. It also indicates the kinds of social and professional support necessary to make this work. (Contains 1 figure and 1 note.)