Purpose: This study examines learning, and both cognitive and behavioral change among a sample of randomly assigned urban principals, half of whom participated in a sustained, district-based professional development program (DPD). Research Methods: Latent class analyses of daily log data, qualitative typology development, and case studies of change provide a rich portrait of the learning and change process. Findings: Few dramatic transformations of practice. Instead, principals attributed to the DPD a gradual refinement of existing practice through a process that allowed them to "break down" declarative knowledge to better understand its consequences for their work, but also provided knowledge structures, tools, and routines for reintegrating ideas from the program into strategically valuable procedural knowledge. Implications: Results suggest potential for developing principals' competencies within continuing practice communities, but expectation of incremental rather than a dramatic "turn around" in principals' leadership through program interventions. (Contains 3 tables, 1 figure, and 4 notes.)