Recent experimental research has shown that women facing the chronic stress of being at familial risk of breast cancer have greater neuroendocrine reactivity responses to stressful laboratory tasks. Whether this enhanced stress response also occurs outside the laboratory under daily life conditions is unknown. In the present study, urinary epinephrine and norepinephrine excretion rates at work (e.g. 11:00 AM-3:00 PM), home (e.g. 6:00 PM-10:00 PM) and during sleep (e.g. 10:00 PM-6:00 AM) were compared between 73 employed women with family histories of breast cancer in first degree relatives (FH+; age=36.8±8.7) and 81 without such family histories (FH-; age=38.1±9.4). Differences in sympathetic adrenal medullary responses to an ordinary life stressor (work) were assessed in naturalistic settings. Repeated measures MANCOVA with family history group as a fixed factor, body mass index as a covariate and daily microenvironment (work, home and sleep) as a repeating factor were conducted to evaluate whether catecholamine excretion rates differed between FH+ and FH- groups. The results revealed that women with family histories of breast cancer had a higher rate of epinephrine excretion while at work (p<0.005). In addition, women in the FH+ group were also more reactive to the stress of work, showing a greater percentage of increase in both epinephrine and norepinephrine from sleep to work (p<0.05). The results also indicated that the chronic stress effects associated with a family history of breast cancer were moderated by BMI, such that their impact was more pronounced and apparent when women were not obese. These findings support the idea that the heightened neuroendocrine reactivity to experimental stressors in women at familial risk of breast cancer also occurs when women encounter stressors in ordinary life (work stress). Additional research to explore the health consequences of increased reactivity in women at familial risk of breast cancer, and perhaps in individuals at familial risk of other life-threatening disease, would appear warranted.