Racial/ethnic disparities in the quality of care provided to mothers and infants during the birth hospitalizations result directly in avoidable death and morbidity. Asian American and Pacific Islanders (AAPI) represent the fastest growing racial/ethnic group (25% living in California) and they experience significant disparities in several areas that are robust and merit policy and clinical attention. Unfortunately, research of AAPI populations suffers considerable limitations. First, few studies report on AAPI populations and those that do, usually aggregate to “Asian” or “Asian American and Pacific Islander”, masking the biological and sociocultural heterogeneity. Sec- ond, sociodemographic and neighborhood factors are rarely available for studies of hospital quality at childbirth. Third, lack of multilevel adjustment undermines the validity of comparative assessments of quality by penalizing hospitals that care for vulnerable populations. To understand disparities in care processes and outcomes for AAPI mother/infants, we will undertake a compre- hensive appraisal of the multilevel factors associated with quality of care during the birth hospitalization, promote fairer comparisons by making sociodemographic and neighborhood influences explicit; and assess key areas of quality using key performance metrics for care provided to mothers, low-risk newborns, and infants born very low-birth-weight (VLBW; <1500g). Innovative methods include leveraging our unique multilevel data sources to provide comprehensive assess- ments of hospital quality for AAPI populations with unprecedented granularity, assessing quality via key indi- vidual and composite measures, and using a mixed-methods approach to provide unique insights into the mechanisms by which sociocultural and neighborhood factors optimize or degrade quality. Specific aims: 1) Test for disparities in care processes and outcomes among AAPI mothers and infants and identify associations with patient and neighborhood level social risk factors; 2) Assess the impact of hospital performance on care processes and outcomes of AAPI maternal/infant popula- tions; and 3) Understand the birth and birth hospitalization experiences of AAPI populations alongside drivers of disparities in care processes and outcomes. An exceptional strength of our proposal is our ability to leverage the unique infrastructure of the California Peri- natal and Maternal Quality Care Collaboratives. Building on our prior work in linking complimentary high-quality clinical, administrative, and survey-based data sets containing multi-level factors, we will study a large popula- tion-scale AAPI sample of 1.6 million mothers and newborns (including ~8,000 VLBW infants) in 238 maternity hospitals and 138 neonatal intensive care units in California between 2011-23. Results of this proposal are expected to have an immediate positive impact because in leveraging our expertise as active quality improve- ment organizations, they are designed to...