Background: The quality of one's marital relationship is gaining recognition as a potential stressor associated with negative health outcomes. Purpose: In this study, we estimated the relationship between marital-role quality and three psychobiological stress indicators (self-reported stress, cortisol levels, and ambulatory blood pressure). Method: Participants were 105 middle-age adults (67 men, 38 women) who had previously taken part in the Whitehall psychobiology study. Ambulatory monitoring and saliva sampling were carried out over a working day, and marital relationships were assessed with the Marital/Partner Role Quality scales. Results: We found that marital-role concerns (but not marital-role rewards) were related to all three psychobiological stress indicators; results did not vary by gender Specifically, participants with more marital concerns reported greater stress throughout the day (p =.014), showed an attenuated cortisol increase following waking (p =.042) and a flatter cortisol slope over the day (p =. 010), and had elevated ambulatory diastolic blood pressure over the middle of the workday (p =.004), with a similar trend in systolic pressure (p =.069). Conclusions: The results suggest that in addition to the carryover of work stress into domestic life that has been evident for many years, there are also influences of domestic strain on biologicalfunction over the working day and evening. Previous research suggests that a possible mechanism linking troubled marriages to health outcomes is depressed immunefunctioning. This study suggests a second mechanism-poorer stress-related biological response.