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The aim of our investigation was to assess blood pressure (BP) and heart rate (HR) variations in 20 essential hypertensive male inpatients (WHO class I and II) and in 20 normotensive healthy volunteers submitted to three provocation tests: isometric handgrip (IHG), bicycle ergometric exercise (BEE) and tyramine infusion (TI) given as i.v. boluses with saline in a single-blind manner. According to our data, IHG induced a comparable rise of systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate in both hypertensive and normotensive subjects. BEE, compared with IHG, caused a more significant (p less than 0.01) rise in SBP and heart rate in both groups. By contrast, DBP during BEE increased significantly in hypertensive (p less than 0.01), but decreased slightly in normotensive subjects (p = n.s.). TI caused a dose dependent SBP rise in both groups studied, while DBP and HR were unaffected. BP elevation was, however, more marked in hypertensive subjects. Confirming this finding, significantly lower tyramine doses were required to produce the same SBP increase in hypertensive patients than in the normotensive volunteers. In short, an SBP rise during TI, and a DBP rise during BEE may be the markers of enhanced cardiovascular reactivity on the part of hypertensive subjects. Our study suggests that BP reactivity to stress may be different according to the laboratory stress employed and also that BEE and TI are more useful than IHG for the assessment of enhanced cardiovascular response to stress in hypertensive subjects.