This working paper assesses the representativeness of the Fragile Families and Child Wellbeing Study sample. It compares the demographic, socioeconomic, and health characteristics of children and families participating in the Fragile Families Study to those of the children and families participating in the Early Childhood Longitudinal Study, Birth Cohort of 2001 (ECLSB). Although the characteristics of the children and families from the Fragile Families Study were generally similar to those of the children and families from the ECLS-B, there were important differences between the samples of these two studies. Families in the Fragile Families Study reported lower household incomes and parents reported lower earnings, fewer years of completed education, and were more likely to be African American and less likely to be non-Hispanic white. Differences between the Fragile Families Study and ECLS-B samples reflect the competing strengths and weaknesses of their respective sampling and data collection strategies.