The goal of the present study was to examine associations among parent perceptions of child care stability during the prekindergarten year and behavioral outcomes (i.e., externalizing and internalizing problems) that same year and during the early elementary grades in a sample of children from low-income households. A second aim was to explore the extent to which the relation between parent perceptions of child care stability in prekindergarten and externalizing and internalizing behaviors in the early elementary years is mediated by prekindergarten behavior problems. Data were obtained from the Head Start Impact Study. The sample included 4442 children (50% male) who were eligible for Head Start. At the start of prekindergarten, children were on average a little over 4-years-old (M = 4.16 years, SD = 0.43). The sample was ethnically/racially diverse and had a range of maternal education levels. Data were collected at baseline (fall of 2002) and in the spring of prekindergarten, kindergarten and 1st grade. (author abstract)