Background Currently, affordability of healthful diets for families is disputed in the research literature. Additionally, no research to date has comprehensively-operationalized or investigated how a set of social-contextual food purchasing influence constructs of parents and children (i.e., cooking ability, concern for nutrition, cost, family food preferences, social pressure, store access, and time) is associated with home food environment, child dietary, and parent and child weight outcomes. Aims (1) Systematically review affordability of a healthful diet in the United States. (2) Develop new purchasing influence measures. (3) Assess possible sociodemographic differences in the new measures. (4) Evaluate relationships between the new measures and home food environment, child dietary, and parent and child weight outcomes. (5) Examine how the new measures explain variance of outcomes when accounting for known potentially influential variables. Design/Sample Aim 1: A systematic data search and evaluation of market basket survey (MBS) research. Aims 2-5: Secondary-data analysis of baseline data of families in the HOME Plus trial. Method Aim 1. MBS methodology, price and affordability findings, and limitations were systematically reviewed. Aim 2-5. Guided by research literature and the social ecological framework, exploratory factor analysis was used to operationalize the purchasing influence constructs. Bivariate and multivariate analyses were used to assess relationships between new measures and outcomes. Results Aim 1. Diets meeting dietary recommendations are potentially unaffordable for low-income families, especially if purchased from small/medium-sized stores. Aim 2-5. Nineteen social-contextual food-purchasing influence measures were developed. In bivariate, multivariate, and hierarchical blocked regression models, many measures within the time, cooking ability, store access, and nutrition concern constructs were significantly associated with home food environment outcomes and to a lesser extent with dietary and weight outcomes. Conclusion Affordability of a healthful diet was called into question for low-income American families. Purchasing influence research findings indicate many social-contextual food-purchasing influences were associated with home food environments. Future, more highly powered research should validate measures and consider longitudinal evaluation and potential intervention, especially related to the time, cooking ability, concern for nutrition, and store access constructs, to improve home food environments, and ultimately, dietary intake and obesity.