Existing developmental models of effortful control focus more on the roles of child characteristics and parenting and focus less on the contributions of poverty-related stressors to individual differences in children's self-regulatory competence. Using a representative sample of low-income, predominantly African American and Latino children (n = 439), the author examined effortful control at ages 2-4 and again 16 months later. Delayed gratification showed moderate stability and improvement over time. Risk factors were associated with individual differences in these developmental patterns, net of child age, gender, temperament, and child-mother connectedness. Low birth weight compromised preschoolers' delayed gratification and executive control. Exposure to more sociodemographic and residential stressors jeopardized children's executive control but did not jeopardize delayed gratification.