Previous studies on the impact of day care center attendance on child development have focused on quantitative aspects (e. g., capacity of the center). Yet the quality of a day care center is also relevant and is increasingly being discussed in the context of day care expansion. The discussion is often limited, however, to improving children?s skills and rarely addresses their health, although this is a key factor in their age-appropriate development. A study by DIW Berlin using data from the Socio-Economic Panel Study (SOEP) and official child and youth services data (KJH-Statistik) shows that regional differences in the quality of day care centers affect the development of children?s health. Preschool children attending a day care center with a high child-staff-ratio are more likely to be sick at the age of five and six. The study also demonstrates that entering early childhood care at four years of age or later increases the probability of illness at the ages of five or six, compared to children attending at a younger age.