To investigate the relationship among systolic blood pressure (SBP) during exercise (EX), left ventricular hypertrophy (LVH) and plasma norepinephrine concentration (NE) in patients with essential hypertension (HT), 20 patients with HT and 20 age- and sex-matched normal subjects were studied using treadmill testing. According to the change in SBP from rest to EX (delta SBP), patients with HT were classified into two groups (group I, n = 12, delta SBP less than 72 mmHg: group II, n = 8, delta SBP greater than or equal to 72 mmHg). There were no significant differences between the two groups with regard to SBP at rest, NE at rest and NE on EX. However, SBP at peak EX, delta SBP and the incidence of LVH were greater in group II than in group I. We conclude that exaggerated SBP response to EX in patients with HT is related to LVH.