Most of his research has focused on racial/ethnic and socioeconomic disparities in health and health care. He is currently directing major projects sponsored by the Agency for Health Research Quality (AHRQ), National Institutes of Health, National Institute of Child Health and Human Development (NIH/NICHD), and Robert Wood Johnson Foundation (RWJF) related to racial/ethnic disparities in health care or health. He is a strong proponent for the development and implementation of quality measures to assess health care for vulnerable populations and the use of quality improvement to address these disparities.