To evaluate the effect of acute blood pressure (BP) changes on the myocardial perfusion in hypertensives, 10 patients with and 10 patients without left ventricular hypertrophy (LVH) were examined with 99TCm-Sestamibi scintigraphy at rest and after acute pharmacological BP reduction using nifedipine and captopril. Signs of LV ischaemia was quantified as the size of the hypoperfused area defined as isotope uptake below 70% of maximum LV uptake, and LVH was defined as ventricular mass (LVM) > 125 g/m2 BSA by use of echocardiography. Not significant relations between BP and size of the hypoperfused area was found at rest. During BP reduction patients with LVH had negative correlations (r = -0.58) between the size of the hypoperfused area and the systolic blood pressure (SBP) and the diastolic blood pressure (DBP) (r = -0.49) while patients without LVH showed positive correlations (SBP r = 0.60, DBP r = 0.48). The differences in correlation coefficients were significant (P < 0.01) for both. Thus, in hypertensives with LVH, ischaemia may develop at low BP providing a possible mechanism for the observed increased risk of cardiovascular events in some hypertensive patients with low achieved BP during follow-up. Until treatment goals are defined on scientific grounds, BP should not be decreased below 90 mm Hg in subjects with LVH.