Research conducted with non-Hispanic Whites indicates that parents of preschoolers with behavioral problems are more likely to have an external locus of control regarding parenting than parents whose preschoolers are free of such problems. However, it is unclear whether such research can be generalized to Mexican American families, especially given research suggesting that Mexican Americans tend to have a more external locus of control normatively. To address this question, the authors compare parental locus of control (PLOC) among parents of clinic-referred Mexican American preschoolers to parents of nonreferred Mexican American preschoolers. Results demonstrate that referred Mexican American parents exhibited a more external PLOC than nonreferred Mexican American parents across a number of domains. Thus, similar to non-Hispanic Whites, preschoolers' behavioral problems are associated with an external PLOC among Mexican Americans. Implications for the design of culturally sensitive interventions for Mexican American preschoolers with behavior problems are discussed. (Contains 4 tables.)