Adverse childhood events can influence the development of emotional and physiological self-regulatory abilities, with significant consequences for vulnerability to psychological and physical illness. This study evaluated stress sensitization and inoculation models of the impact of early parental death on stress exposure and reactivity in late adolescence/young adulthood. Ambulatory blood pressure (BP) and diary reports of minor stress were collected every 30 min during waking hours over a 24-hr period from 91 late adolescents/young adults (43 early bereaved, 48 nonbereaved). Across the sample, minor stressors were associated with elevated BP and negative affect. The bereaved group had lower BP than did the nonbereaved group. Within the bereaved group, higher perceived caring from the surviving parent was associated with fewer reports of minor stress and lower stress-related negative affect. Higher perceived parental caring during childhood was associated with lower BP across the sample and more frequent hassles in the nonbereaved group. Findings support both the stress inoculation and sensitization models, suggesting that childhood parental loss and parental caring exert important influences on children's development of stress sensitivity. (Contains 1 table, 2 figures, and 1 footnote.)