Objectives. Although higher quality marriages are associated with better health outcomes, less is known about the mechanisms accounting for this association. This study examines links among marital/partner quality, stress, and blood pressure and considers both main and moderating effects.Method. Participants from the National Social Life, Health, and Aging Project (N = 1,854; aged 57–85 years) completed in-person interviews regarding their marital/romantic partner relationships and perceived stress. Interviews included blood pressure assessments.Results. Linear regression models revealed no main effects of spousal/partner quality or stress on blood pressure. However, spousal/partner quality moderated the link between stress and blood pressure. Specifically, there were negative associations between stress and blood pressure among people reporting more confiding, less reliance, and greater demands from spouses/partners.Discussion. Findings highlight the complexity of relationship quality. Individuals appeared to benefit from aspects of both high- and low-quality spouse/partner relations but only under high levels of stress. Findings are inconsistent with traditional moderation hypotheses, which suggest that better quality ties buffer the stress–health link and lower quality ties exacerbate the stress–health link. Results offer preliminary evidence concerning how spousal ties “get under the skin” to influence physical health.