Abstract Children with nonorganic failure to thrive (NOFTT) comprise a population at risk for small stature, poor growth, slower development, and lower intellectual outcomes. These children are often seen in the Women, Infants, and Children Supplemental Nutrition Program (WIC) and child health clinics and in caseloads of high-risk families. Public health nurses may not be sure how to intervene in the problem of NOFTT because of its multifactorial etiology. A model of nursing care that addresses the many factors that affect the development of NOFTT can enable the public health nurse to appropriately care for the child with NOFTT. The Eco-Epi model, a combination of human ecology and epidemiology, is a conceptual model that can provide a framework for the public health nurse to plan interventions. Even though children with NOFTT are the target population for this model, it can be applied to other public health nursing populations at risk for multifactorial problems. In the Eco-Epi model, the epidemiological concepts of agent (food), host (child), and environment (home) are examined in the context of the microsystem (parent-child interaction, daily activities of the family), the mesosystem (interactions between different environments), and the exosystem (the child's community). The concepts of microsystem, mesosystem, and exosystem are from the theory of human ecology. Examples of how the model works to assess a family and design interventions are provided.