Ecological models of human interaction can be used to study complex community problems that affect health disparities. These models allow researchers to study the components of a problem and understand how the problem can be ameliorated with nursing interventions. This article describes four research studies in which ecological models were used to either understand a phenomenon or design and test an intervention. The methods used were ethnography, descriptive/correlational, and quasi-experimental. All subjects were low-income women and children, largely of Hispanic ethnicity, residing in South Texas. The ecological models were derived from Bronfenbrenner's ecology of human development theory, epidemiology, Rubin's theory of developmental tasks of pregnancy, and Barnard's model of mother-child interaction. Heuristic models that represent reality allow researchers to divide a complex problem, such as health disparities, into manageable components. The influence of families, neighborhoods, and communities can be considered without losing sight of individuals.