The repeated activation of physiological stress systems in response to the chronic stress associated with poverty in early childhood signals environmental instability, leading to changes in patterns of physiological response that appear to prepare children for future stress. Consistent with an ecological model, poverty creates environmental instability across children's developmental contexts. Families differ in their psychological distress in response to poverty related stressors. Such differences in response (reflective of parental psychological wellbeing) may intensify or buffer the child's perception of environmental instability. This dissertation study tested the hypothesis that children show distinct profiles of physiological response (Sympathetic Nervous System and Hypothalamic Pituitary Adrenal axis activity) when challenged with a socially evaluative stressor using a sample of 156 children attending a Head Start preschool program. Latent profile analysis results confirmed the existence of 4 distinct profiles: Multisystem Responder, Low sAA Activity, Heightened sAA Responder, and Moderate sAA Responder. Multinomial regression analyses suggested family level stressors (parenting stress, poverty-related stressors, and their interaction) predicted profile group membership, in addition to caregiver employment status and gender. Results and implications for research and intervention are further discussed. (author abstract)