The major complications in sickle cell disease (SCD) are microcirculation lesions and impairment of renal function. The aim of this study was the evaluation of renal vascular resistance by means of spectral pulsed Doppler sonography and its relationships with haematological and clinical features in patients with SCD. 40 patients with SCD (mean age 22.4+/-7.0) and 14 age and sex matched healthy subjects (mean age 25.7+/-9.5) were included into the study. Spectral Doppler sonography of main renal, segmental and interlobar arteries were performed on both kidneys in all patients and controls. Peak systolic, end diastolic and mean velocities through the entire cardiac cycle were obtained, with calculation of the resistive (RI) and pulsatility (PI) indices. All the patients were investigated in stable state conditions and had not been transfused within a month before investigation. Patients were followed for up to 6 months. Patients with SCD had higher values of RIs and PIs than control subjects (p<0.0001, p<0.0001, respectively). Patients with high value of RIs (RI>0.70) had more pronounced disturbances of blood parameters (all p<0.05), than patients with normal RIs (RI<0.70). Significant positive correlation existed between RIs and ISC number, MCHC level (r=0.52, p<0.001 and r=0.42, p<0.01), while RBC count and Hb level correlated inversely with RIs (r=-0.39, p<0.01 and r=-0.42, p<0.01). During follow-up, nine patients (33.3%) with high RIs and only one patient (5.5%) with normal RI developed painful crises. In conclusion, renal vascular resistance, assessed by Doppler sonography was raised in SCD patients as compared with age matched apparently healthy persons. These changes were more pronounced in those with more severe manifestations of disease and correlated with haematological and clinical features of sickle cell disease.