Ambulant 24 h blood pressure was recorded in 97 untreated hypertensive subjects (50 with, 47 without echocardiographic signs of left ventricular hypertrophy) and 45 matched normotensive subjects. Forearm vascular resistance was calculated from mean blood pressure and blood flow, which was measured by venous plethysmography during reactive hyperemia. Blood pressure variability was calculated by standard deviations of pressure values. Systolic 24 h blood pressure exhibited the closest correlation with left ventricular mass index in hypertensives (4 = 0.48; P < .001). No relation could be found between blood pressure fall during the night and left ventricular mass index. Furthermore, body weight was a significant correlate of left ventricular mass (r = 0.53; P < .001). Regression analysis indicated that body weight and 24 h blood pressure were the principal determinants of left ventricular mass. Blood pressure variability was significantly higher in hypertensive than in normotensive subjects (P < .05). The highest vascular resistance was found in hypertensive patients with left ventricular hypertrophy compared with the other groups (P < .05). A significant close correlation between systolic resting as well as 24 h blood pressure and vascular resistance was identified for the group of hypertensives and all subjects investigated. Furthermore, left ventricular mass index and vascular resistance were correlated (in hypertensives: r = 0.32; P < .01). The extent of left ventricular mass index and forearm vascular resistance are proportional to the severity of hypertension. As vascular resistance and left ventricular mass are also related, these findings could speak for a parallel development of total peripheral resistance and left ventricular hypertrophy in essential hypertension.