In order to avoid interpretation problems relating to the impact of reproductive hormones on cardiovascular variables, research on the psychosomatic etiology of cardiovascular disease frequently excludes women who use oral contraceptives (OCs), and sometimes women as a whole, from study samples. However, such conventions are based on a body of research that suffers from methodological limitations and, in any event, has produced inconclusive findings. Further, the relevant research fails to control for personality differences between users and non-users of OC that may, in turn, lead to differences in stress reactivity. In the present study, using a counterbalanced mixed-factorial design, 24 women (12 OC users and 12 non-users), drawn from a screening sample of 110, were tested across a 4-month timeframe. Cardiovascular reactivity (CVR) was measured during both the follicular and luteal phases of each woman's menstrual cycle. Menstrual phase and OC use were found to exert synergistic effects on CVR. A significant relationship between neuroticism and systolic blood pressure reactivity was observed, which was found to be contingent on menstrual phase. It is concluded that while menstrual phase and OC use are relevant, their contaminating influence on CVR research can be circumvented.