This study was conducted to gain insight into individuals' perceptions of their willingness and ability to change their nutrition behavior. As eating habits are primarily socially learned, the locus of control theory, a social learning theory, was applied to the understanding of nutrition behavior. Responses from 105 young male and female subjects to a questionnaire devised to examine individuals' beliefs about the internal and external factors which control, or determine, dietary habits and health were analyzed. Individual values and assessment of personal health and diet were measured, and demographic data were collected. Two major findings were obtained. First, the locus of control theory was too narrow a construct to explain the subjects' responses and beliefs. The data suggested six categories which differentiated between individuals' expectations about factors controlling outcomes of behavior and those controlling actual personal behaviors. Second, there were significant differences in responses to locus of control statements on the basis of certain demographic variables, especially religious affiliation. Religious/traditional Jewish subjects tended to be more internally oriented than nonreligious/nontraditional Jewish subjects, independent of other demographic variables. Subjects with greater willingness and perceived ability to change their nutrition behavior appeared to take responsibility for choosing what is "right" or "better" and had firmly established personal guidelines for what is, or is not, acceptable.