Structural vascular changes in the calf arteries and left ventricular mass were measured in 52 essential hypertensive patients (WHO I and II, 35 men and 17 women, age range 21-63 years). Left ventricular mass was measured on M-mode echocardiographic tracings. Structural vascular changes were evaluated indirectly by studying the minimal vascular resistance, calculated from mean arterial pressure and maximal (post-ischaemic) blood flow, measured by venous occlusion plethysmography. A statistically significant correlation between left ventricular mass and minimal vascular resistance was observed (r = 0.33, P < 0.05). The low correlation suggested that structural changes in the heart and in the systemic arteries did not develop simultaneously. In the subgroup of patients with minimal vascular resistance in the normal range, left ventricular hypertrophy was found in 15 out of 30 patients (50% of cases) whereas, in the subgroup of patients with high minimal vascular resistance, absence of left ventricular hypertrophy was found in six out of 22 patients (27% of cases). These results suggest that left ventricular hypertrophy more often precedes arterial structural changes in the calves.