This report is the first part of an affordable housing needs assessment for the DC Office of the Deputy Mayor for Planning and Economic Development. We examined the District of Columbia’s Inclusionary Zoning (IZ) program through interviews, document review, and data analysis. The IZ program has great potential to help expand the city’s supply of affordable housing, particularly in neighborhoods undergoing rapid development. While the overall design of DC’s IZ program seems sound, we believe that adopting the proposed IZ administrative regulations will help developers, renters, and owners save time and improve their understanding of the program and its requirements.