Twenty "hypertensive" 18-year-old men (systolic BP greater than or equal to 146 and/or diastolic BP greater than or equal to 90 mmHg) from the screening examinations of a military draught bureau were compared with 17 normotensive (systolic BP 124-131) and 12 hypotensive (systolic BP 100-106) subjects. The hypertensive subjects were on average taller, showed more often ECG evidence of sympathoadrenomedullary overactivity, tended to excrete more adrenaline in the urine during a standardized psychological stress test, had higher serum levels of sodium and potassium and reported more frequently family prevalence of hypertension than the normotensives and hypotensives. Non-participating subjects without verified hypertension had higher mean relative weight than any of the study groups. Only one hypertensive subject showed dilated pulmonary vessels on chest X-ray and borderline evidence of mild left ventricular hypertrophy. None of the hypertensive subjects showed evidence of decreased glomerular filtration rate or endocrine disorder. The subjects in both comparison groups showed frequently ECG evidence of parasympathetic activity. The hypotensive group had a lower average relative body weight than the other groups.