The presence of supportive others has been associated with attenuated cardiovascular reactivity in the laboratory. The effects of the presence of a spouse and others in a more naturalistic setting have received little attention. Blood pressure and heart rate reactions to mental stress were recorded at home in 1028 married/partnered individuals. For 112 participants, their spouse/partner was present; for 78, at least one other person was present. Women tested with a spouse/partner present showed lower magnitude systolic blood pressure and heart rate reactivity than those tested without. Individuals tested with at least one non-spousal other present also displayed attenuated reactivity. This extends the results of laboratory studies and indicates that the spontaneous presence of others is associated with a reduction in cardiovascular reactivity in an everyday environment; spouse/partner presence would appear to be especially effective for women.Key words: acute stress, blood pressure, presence of spouse/partner, pulse rate, reactivity, social support 3 Exaggerated cardiovascular reactions to acute psychological challenge are considered a risk factor for cardiovascular pathology (Lovallo & Gerin, 2003;Schwartz et al., 2003) and several prospective studies have now shown consistently that high reactivity confers a modest additional risk for elevated blood pressure and other cardiovascular outcomes (e.g. Carroll, Ring, Hunt, Ford, & Macintyre, 2003;Markovitz, Raczynski, Wallace, Chettur, & Chesney, 1998;Treiber et al., 2003). In addition, a number of epidemiological studies have shown that social support is negatively associated with morbidity and mortality (e.g. Berkman & Syme, 1979;House, Robbins, & Metzner, 1982;Orth-Gomer & Johnson, 1987;Rosengren, Orth-Gomer, Wedel, & Wilhelmsen, 1993); marriage, strong social ties, and emotional support from others have all been linked to better general, including cardiovascular, health outcomes (e.g. Gordon & Rosenthal, 1995;Marmot et al., 1975;Robles & Kiecolt-Glaser, 2003;Verbrugge, 1979). It has been hypothesised that social support may enhance cardiovascular health, at least in part, by attenuating the cardiovascular reactions to stress exposure (Kamarck, Peterman, & Raynor, 1998;Smith & Gerin, 1998).A number of studies have now tested the proposition that the presence of supportive others attenuates cardiovascular reactivity (Lepore, 1998). A range of paradigms have been employed, but virtually all studies, for convenience, have tested student samples, particularly female students. For the most part, studies that have examined the effects of active social support have had students give a speech, usually on a controversial topic, and compared cardiovascular reactions to this task in different social contexts: alone, with challenging or non-supportive others present, with actively supportive others present. In general, those with supportive others present exhibited lower reactivity than those tested in other conditions (Christenfeld et al., 1997;Gerin, Pieper, Levy,...