Objective: To evaluate the hemodynamic and other general determinants of the renal resistive index (IRR) in a group of middle age hypertensive subjects. Design and method: The population of our study were 62 patients (34 females and 28 males, mean age 45,26 years +/- 5,2 years) with grade I-II arterial hypertension. All subjects underwent careful clinical history and physical examination. A complete echocardiographic study, ambulatory blood pressure monitoring and color Doppler ultrasound of renal and intrarenal arteries were performed to all of the subjects. Intrarenal Doppler measurements were repeated in three parts of both kidneys (superior, median, and lower) untill three reproducible waveforms were obtained. RRI was calculated with the following formula: (peak systolic velocity – end diastolic velocity)/peak systolic velocity, and the mean value of three measurements at each kidney was considered. Results: The mean RRI was 0,678 ± 0,092, mean daytime ambulatory systolic blood pressure (SBP) was 141,96 ± 16,04 mmHg, mean nighttime SBP was 131,46 ± 17,36 mmHg, mean 24 hours SBP was 136,91 ± 19,09 mmHg, mean daytime ambulatory diastolic blood pressure (DBP) was 82,07 ± 18,93 mmHg, mean nighttime DBP 71,92 ± 26,80 mmHg mean 24 hours DBP 77,10 ± 22,4 mmHg. The mean pulse pressure (PP) was 59,10 ± 22,90 mmHg. The mean 24 hours heart rate (HR) was 75,14 ± 26,86 beats/minute. RRI was negatively related to ambulatory 24 hours DBP (r = –0339, p = 0,05), mean nighttime DBP (-0,299, P < 0,01), HR (r = –0,326, p < 0,01) while it was positively associated with ambulatory 24 hours SBP (r = 0,659, p = 0,05), mean daytime SBP (0,560, p < 0,05) ambulatory PP(r = 0,366, p < 0,01), age (r = 0,253, p < 0,01), left ventricular mass (LVM) (r = 0,459, p < 0,01) and relative wall thickness (RWT) (r = 0,493 p < 0,01), statistically signifi cant even after adjustment for various confounding factors. In multiple regression analysis, mean 24 hours SBP, daytime SBP, PP (p < 0.01) and LVM (p < 0.05) were revealed as main determinants of RRI. Conclusions: The interaction between the systemic hemodynamics and the intrarenal circulation is a complex physiological phenomenon. In addition to renal vascular properties, the central hemodynamic factors signifi cantly infl uence the intrarenal arterial patterns.