1. Plasma noradrenaline, active and inactive plasma renin, cardiac index and total peripheral vascular resistance were studied in 41 subjects, initially aged 10–19 years, who were followed up for at least 2 years after a blood pressure reading of 140 and/or 90 mmHg or more (initial hypertensives) and in 41 normotensive control subjects selected from the same population and matched for age, sex and body-mass index. 2. The initial hypertensive subjects had a lower mean cardiac index (3.63 ± sd 0.83 vs 4.00 ± 0.89 litre min −1 m −2 ), a higher mean total peripheral resistance (26.8 ± 5.7 vs 22.8 ± 5.5 units) and a higher mean plasma noradrenaline concentration (336 ± 146 vs 281 ± 126 pg/ml) than the control subjects. 3. Mean plasma noradrenaline concentration was higher in initial hypertensive subjects with a high active renin concentration than in those with a normal renin concentration (442 ± 70 vs 324 ± 100 pg/ml). 4. A weight-adjusted standardized regression coefficient of 0.77 between active plasma renin concentration and left ventricular mass was found in normotensive control subjects. 5. These findings are at variance with the existence of a hyperkinetic phase in young hypertensive subjects and suggest that sympathetic overactivity may be related to early essential hypertension through increase of peripheral vascular resistance.