To evaluate the correlations among Doppler sonographic findings, morphologic sonographic findings, and laboratory findings representing renal functional status, duplex Doppler sonography of the kidney was performed in 32 patients with diabetes mellitus. Resistive indices obtained in the region of the arcuate or the interlobar arteries in patients with elevated serum creatinine levels were significantly higher than those in patients with normal serum creatinine levels (P < 0.05). Also, there was a significant correlation between the resistive indices and creatinine clearance levels (correlation coefficient, -0.828). There was a significant difference between the serum creatinine levels of patients with normal renal cortical echogenicity and those with increased cortical echogenicity (P < 0.05). Analysis of the Doppler spectrum of the intrarenal arteries in conjunction with careful evaluation of the renal cortical echogenicity may be helpful in sonographic prediction of the renal functional status in patients with diabetes mellitus.