As a result of policy changes following welfare reform in 1996 and the costs associated with providing high-quality early care and education for children of low-income working families, agency collaboration in the state of Illinois has become an increasingly salient feature of subsidized early care and education programs (SECE). The authors examine how the three major subsidized early care and education programs in Illinois collaborate to meet the diverse needs of low-income children and families. Based on an in-depth literature review and semistructured interviews with state and local stakeholders, the authors find that collaboration in the SECE system is frequent, despite different program eligibility criteria, guidelines, performance expectations, perspectives on quality measures, and mechanisms for monitoring. However, the extent to which collaboration occurs is not well understood, which may affect how stakeholders interpret the impact of publicly funded early care and education programs. This may prevent accurate characterization of children's early care and education experiences and hinder assessments of how such experiences impact their development. (author abstract)