Background and Objectives: Previous research indicates that early life adversity may heighten stress reactivity and impair mechanisms for adaptive coping, suggesting that experience of stress in early life may also potentiate adults' physiological vulnerability to stress in later life. The study tested this hypothesis by investigating whether experience of stressful events and circumstances (SEC) in childhood or adolescence amplified the effect of adulthood SEC on physiological dysregulation (allostatic load, AL) in later midlife. Design: Observational data were used in the present study. Physiological functioning was measured in later midlife (participants' age ranged from 49 to 63). Both childhood/adolescence and adulthood SEC were reported retrospectively on the same occasion. Methods: Participants were 5,309 Danish men and women from Copenhagen Ageing and Midlife Biobank. SEC included socio-economic and family factors. The AL index was based on 9 cardiovascular, metabolic and immune biomarkers. Results. Experience of SEC in both early life and adulthood independently predicted higher AL. In men, experience of SEC in early life also potentiated the effect of SEC in adulthood on AL. Conclusions: The results provide further insight into the mechanisms behind the "biological embedding" of childhood stress.