Conflito de interesses: Não Abstract Introduction:In recent years, childhood mortality rates have been decreasing in Brazil. However, morbidity remains a challenge, especially among low-income families. These children are vulnerable because they are more exposed to various biological and environmental risk factors. Objectives: Investigate the prevalence of infectious and chronic diseases in children attending public day-care centers and characterize the risk factors involved. Patients and Methods: This is a descriptive cross-sectional study involving all children between the ages of 24 and 36 months attending public child day-care centers in two cities in the Jequitinhonha Valley and their caregivers, in 2011. We developed a questionnaire o collect children's sociodemographic and biological characteristics. The environment of the neighborhood was assessed by the existing infrastructure. The home and the public child day-care centers environment were evaluated by indicators extracted from the Home Inventory and Infant/Toddler Environment Rating Scale-Revised, respectively. Results: Of the participants, 47% had some infectious disease, while 44% had a chronic disease. There was a high percentage of female single-parent families; half of the families belong to the economic classes D and E, and about 32% of the mothers had four years or less of schooling. About the environmental context, just a few neighborhoods have acees to basic sanitation; half of the houses and almost every public child day-care centers presented a risk to children's health. Conclusion: Almost half of the children in the study, who were economically disadvantaged, presented infectious and chronic diseases in the last three months preceding the survey. Sociodemographic, biological, and environmental risks were detected. In order to reduce the morbidity among this vulnerable group of children, public interventions are required, as well as policy strategies covering biological and environmental aspects, including greater investment in health education.