The objective of this study was to examine the potential effects of long term hormone replacement therapy on cardiovascular autonomic nervous system responses to laboratory social stressors. The participants were 38 postmenopausal women, 18 using estrogen and progesterone hormone replacement therapy for at least 2 years and 20 control participants without hormone replacement therapy. All women completed orthostasis (standing and sitting), then speech and math tasks (speech and math were counterbalanced). Cardiovascular measures of sympathetic nervous system (pre-ejection period, PEP) and parasympathetic nervous system (respiratory sinus arrhythmia, RSA) along with heart rate were collected throughout all periods (baseline, orthostasis, and stressors). For orthostasis, results of mixed analyses of variance (ANOVAs) showed expected period effects for heart rate, RSA and PEP, but no group or group by period interaction was significant. For the psychological stressors, period main effects were significant for all three variables, suggesting that the tasks were effective at inducing stress. Also, there was a significant interaction between group and period for RSA, demonstrated by greater decrease during the psychological stressor period in the group using HRT. The interactions between group and period for heart rate and PEP were non-significant. These findings support the notion that HRT may slow age-related decreases in parasympathetic responsiveness. Furthermore, changes in vagal reactivity in relation to use of HRT appear to occur within mechanisms involving response and coping with psychological stressors, rather than mechanisms that accommodate basic physiological task such as orthostasis.