Teacher professional development variously supports ongoing skill development, new knowledge, and systems change. In New Zealand, the implementation of major assessment reforms in senior secondary schools provided opportunity to investigate teacher professional development as a function of the particular stage of an educational reform. Multi-method data sources including teacher surveys and school case studies were employed to evaluate professional development during the embedding stage of a standards-based assessment system, revealing a positive relationship between professional satisfaction and teacher involvement in setting priorities for the professional development. Other positive features were networking, personalized learning, and facilitator expertise. This research illustrates the importance of tailoring professional learning to implementation phase of an organizational change. (Contains 1 figure and 6 tables.)