BACKGROUND: Approximately 3.5 million U.S. schoolchildren are limited in English proficiency (LEP). Disparities in children's health and health care are associated with both LEP and speaking a language other than English at home, but prior research has not examined which of these two measures of language barriers is most useful in examining health care disparities. OBJECTIVES: Our objectives were to compare primary language spoken at home vs. parental LEP and their associations with health status, access to care, and use of health services in children. METHODS: We surveyed parents at urban community sites in Boston, asking 74 questions on children's health status, access to health care, and use of health services. RESULTS: Some 98% of the 1,100 participating children and families were of non-white race/ethnicity, 72% of parents were LEP, and 13 different primary languages were spoken at home. "Dose-response" relationships were observed between parental English proficiency and several child and parental sociodemographic features, including children's insurance coverage, parental educational attainment, citizenship and employment, and family income. Similar "dose-response" relationships were noted between the primary language spoken at home and many but not all of the same sociodemographic features. In multivariate analyses, LEP parents were associated with triple the odds of a child having fair/poor health status, double the odds of the child spending at least one day in bed for illness in the past year, and significantly greater odds of children not being brought in for needed medical care for six of nine access barriers to care. None of these findings were observed in analyses of the primary language spoken at home. Individual parental LEP categories were associated with different risks of adverse health status and outcomes. CONCLUSIONS: Parental LEP is superior to the primary language spoken at home as a measure of the impact of language barriers on children's health and health care. Individual parental LEP categories are associated with different risks of adverse outcomes in children's health and health care. Consistent data collection on parental English proficiency and referral of LEP parents to English classes by pediatric providers have the potential to contribute toward reduction and elimination of health care disparities for children of LEP parents.