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Obtaining meaningful baseline measures of children's cardiovascular activity (CVA) has been difficult because of constraints inherent to laboratory procedures that are used to assess individual differences in response to stress. To circumvent these problems, we performed repeated baseline measures of pulse rate (PR) and blood pressure for 174 children (aged 7–10 yr) in their natural school setting throughout 2 1-week periods. In addition, experimental assessments of cardiovascular reactivity (CVR) were conducted after each baseline period while children participated in a challenging cognitive task. Multivariate analyses of physiological indices revealed three primary styles of cardiovascular functioning. Two of them, characterizing children either with high PR and low blood pressure or conversely with low PR and high blood pressure, have already been described in the research literature. However, analyses also revealed a third group of children (48% of the subjects) who had both low PR and low blood pressure. Findings indicate developmental differences in cardiovascular regulation and highlight the need to consider both variations in baseline CVA as well as in CVR when examining children's physiological adaptation in everyday settings.