Marriage reduces risk of cardiovascular disease (CVD) but marital stress increases risk, perhaps through cardiovascular reactivity (CVR). However, previous studies have lacked controls necessary to conclude definitively that negative marital interactions evoke heightened CVR. To test the specific effects of marital stress on CVR, 114 couples engaged in positive, neutral, or negative interactions in which speaking and task involvement were controlled. Compared to positive and neutral conditions, negative discussions evoked larger increases in systolic blood pressure, heart rate, and cardiac output, and larger decreases in peripheral resistance and pre-ejection period--similarly for men and women. Hence, CVR could contribute to the effects of marital difficulties on CVD. Previous evidence of sex differences in this effect might reflect factors other than simple reactivity to negative interactions.