Following findings of cardiovascular hyperactivity to stressful stimuli among hypertensive patients, a psychologic construct of Emotional Reactivity (ER) was formulated as a possible intervening variable. ER was conceived as a tendency to enter an emotional state characterized largely by the extension of psychologic representation of stressful stimuli after their actual termination. The emotionally reactive person was defined as one who experiences intrusive-repetitive images and thoughts following emotional events, lacks control over the tendency to become emotionally aroused despite conscious attempts to do so, becomes emotionally aroused in anticipation of forthcoming emotional events, and experiences excessive magnitude and/or duration of emotional response following an emotional event. Based on these features, a scale measuring ER was developed. The scale was found to be reliable and showed test-retest stability over 1 year. The study population included 837 subjects, divided into controls and those with elevated blood pressure (BP), either systolic (greater than or equal to 140 mm Hg) or diastolic (greater than or equal to 90 mm Hg), on the basis of site measures conducted in the workplace; subjects already receiving antihypertensive medication were included in both the latter groups. The results showed that subjects with elevated systolic BP (SBP) scored significantly higher on the ER scale than the controls and this was true for both sexes. Females with elevated SBP had higher ER scores than males, and this was particularly true for those over 40. Control subjects with a history of familial hypertension scored higher on the ER scale than controls without such a history.