Early Head Start serves pregnant women and children up to age 3, allowing families to enroll a child at any point in this age range. Head Start serves preschool-age children, who can enter the program at age 3 or 4. Engaging and retaining families in the program is a priority for Early Head Start and Head Start. However, some children who enroll in these programs do not stay for the full length of time they are eligible. In this brief, we explore the child-, family-, and program-level factors that may be associated with whether children leave the program early. We used data from the Early Head Start Family and Child Experiences Survey (Baby FACES) and from the 2009 cohort of the Head Start Family and Child Experiences Survey (FACES 2009). Analyses show that most families who enrolled stayed for as long as they were eligible. However, a sizable percentage -- 35 percent in Early Head Start and 27 percent in Head Start left early. Early leaving was only related to a few child, family, or program characteristics examined in this brief. The findings suggest that the rate of early leaving was higher among families with several risk factors and who experienced instability, but mainly for Early Head Start families. In Head Start, early leaving was less associated with family risk and more related to program characteristics; children were more likely to leave early if they attended urban programs, if the turnover rates for lead or assistant teachers were high, and if program directors reported there were factors making it more difficult for them to do their jobs. To fully understand the circumstances related to leaving early and what programs can do to keep children enrolled, it will be important to gather additional data about families' needs and what they opt to do in lieu of participating in Early Head Start or Head Start. (author abstract)