In this study, we used the technique of meta-analysis to address two specific questions: First, is there a relationship between dietary intake and either a) nutrition knowledge or b) food- and nutrition-related attitudes? And second, if there is a relationship, what is the strength (effect-size) of the relationship between these variables? A review of the literature identified nine studies that met our criteria for inclusion in the meta-analysis. We coded the characteristics of each study and then analyzed the data by using two analytic techniques that combine the probability levels associated with a significance test of the relationship between the theoretical variables, and estimated the effect-size of the relationship between the variables. We found a significant relationship between nutrition knowledge and dietary intake and between food- and nutrition-related attitudes and dietary intake, but the effect-size estimates of these relationships were relatively small. These effect-size estimates may reflect a lack of consideration for the dimensionality of the theoretical variables, a lack of validity in the measurement of knowledge and attitudes, and/or a lack of correspondence between the measures of dietary intake and knowledge or attitudes.