Relations of maternal and child characteristics to child cortisol reactivity to and recovery from emotional arousal were examined prospectively at approximately 7 months of age (infancy) and then again at approximately 15 months of age (toddlerhood). The sample was diverse and population based (N = 1,292 mother-infant dyads) and included families from predominantly low-income, rural communities. Maternal behavior, family income-to-need ratio and social advantage, and child temperament, attention, and mental development were assessed, and children's saliva was sampled before and after standardized procedures designed to elicit emotional arousal. Maternal engagement in infancy was associated with greater cortisol reactivity at the infancy assessment and with reduced overall cortisol level at the toddler assessment. Also at the toddler assessment, child attention, mental development, and temperamental distress to novelty were associated with increased cortisol reactivity and regulation, whereas temperamental distress to limitations and African American ethnicity were associated with reduced cortisol reactivity. Findings are consistent with prior work linking early caregiving to the development of the hypothalamic-pituitary-adrenal axis stress response system and with a conceptual model in which developing temperament is characterized by the interplay of emotional reactivity and the emergence of the ability to effortfully regulate this reactivity using attention. (Contains 4 tables and 3 figures.)