Preparing teachers to implement a new curriculum presents a significant but important challenge. While formal professional development programs can assist in this preparation, finding prescribed experiences that meet the needs of all teachers can be formidable and indeed may not always be the best option for promoting change in practice. Decisions about what experiences to provide and how and when to provide them need to be made in an informed manner. Studies such as the one being reported on in this article provide insights into teachers' perspectives on what works and what doesn't work. This research project examined how elementary teachers in one Canadian school district were handling implementation of a new social studies curriculum over the 2009-10 school year, three to five years after they experienced a formal district-level program of professional development. An interpretive case study method was used to uncover the successes and challenges of implementing the new curriculum and to provide insights into what the teachers felt constituted effective professional development for improving practice and student learning. Findings from the study suggest that effective professional development needs to be based on teachers' needs; involve active learning, collaboration and modeling; be supported by a culture of learning in schools; and considerate of teacher resistance to change. Going forward, the study also highlights the need for a more intentional focus on the use of technology, and specifically digital networks, to enhance and extend the effectiveness of future curricular change initiatives. (Contains 10 figures.)