As hypertensive target-organ damage has been associated with diminished diurnal blood pressure (BP) variation in adults, we compared diurnal BP patterns of hypertensive adolescents with left ventricular hypertrophy with normotensive and hypertensive adolescents with normal left ventricular mass. In addition, the frequency of microalbuminuria (Malb), hyperfiltration, and reduced renal functional reserve (RFR) was evaluated in adolescents with normal BP and untreated borderline and mild essential hypertension. Thirty-three normotensive (NT) adolescents, 14.5+/-2.1 years (mean +/- SD), and 29 untreated borderline and mildly hypertensive (HT) adolescents, 14.6+/-2.4 years, wore the SpaceLabs 90207 ambulatory BP monitor for 24 h. Left ventricular mass was measured by M-mode echocardiography and then indexed (LVMI) to the cube of height. Creatinine clearance (Clcr) and urine Malb was measured on 24 h collection and RFR by change in creatinine clearance after an oral protein load. Diurnal BP change was expressed as the absolute and percent day-night BP fall and cusum derived plot height (CPH) and circadian alteration magnitude (CDCAM). Groups were compared using analysis of covariance with adjustments for race, gender, and body mass index. All NT and 19 HT subjects (HT-1) had normal LVMI at 22.2+/-5.3 and 25.8+/-3.8 g/m3, respectively. Ten HT (HT-2) had increased LVMI of 36.9+/-5.2 g/m3. No significant difference was found for absolute or percent day-night BP fall or CDCAM between groups. Nocturnal systolic BP was correlated most closely with LVMI (r = 0.41, p = .001). Clcr, Malb, and RFR did not differ between the groups. In conclusion, adolescents with borderline and mild essential hypertension and left ventricular hypertrophy have similar levels of diurnal BP fall, urine Malb excretion, and RFR compared to normotensive and hypertensive adolescents with normal left ventricular mass.