A large literature has documented the influence of child care on young children's development, but few studies have examined low-income children in community care arrangements. Using data from Welfare, Children, and Families: A Three-City Study (N=204), this study examined the influence of child care quality and the extent of care on low-income children's (ages 2-4 years) cognitive and socioemotional development over time. Higher levels of child care quality were modestly associated with improvements in children's socioemotional development, and extensive hours in child care were linked to increases in children's quantitative skills and decreases in behavior problems. Analyses suggest that child care quality may be particularly salient for subgroups of children from low-income families.