PURPOSE: To compare the RI (resistive index) of renal artery with serum creatinine level and histological change in 50 patients with renal parenchymal disease. MATERIALS AND METHODS: To measure RI in each patient, Doppler studies were performed three times in each kidney at the level of the interlobar arteries, and the average value of RI was taken. The study was performed 1-3 days after renal biopsy and the time interval between blood sampling for serum creatinine and duplex study was also 1-3 days. The RI of patients with renal disease was also correlated with patient's age, sex and serum creatinine level, and RI was also correlated with the degree of severity of glomerular, interstitial, and vascular change in the kidneys. Statistical analysis was performed using Student's t test and Pearson's correlation method. RESULTS: The RI of the normal control and renal disease group was 0.566±0.037 and 0.584±0.038, respectively with no statistical significance (p=0.444). In the group with renal disease, there was no significant correlation between RI and a patient's age, sex, and serum creatininelevel (p>0.05). RI was not significantly different between predominantly glomerular disease (n=45) and nonglomerular or mixed disease (n=5) (p=0.558), and did not correlate with the severity of glomerular sclerosis, interstitial fibrosis, or atherosclerosis (p>0.05). CONCLUSION: The authors conclude that RI is not helpful for the diagnosis and differential diagnosis of renal parenchymal diseases and does not correlate with serum creatinine levels. In order to define the role of the RI, further clinical experience with more cases is required.