Renal failure is an important cause of morbidity and mortality in feline patients. In human patients, intrarenal blood flow values obtained with duplex Doppler ultrasonography have been used to aid in the diagnosis and prognosis of renal failure. The purpose of this report is to present values for resistance to intrarenal blood flow in normal cats, derived by duplex Doppler ultrasonography. Ten mature clinically healthy conditioned domestic shorthaired cats were screened for normal renal anatomy and function by CBC, serum biochemical profile, urinalysis, urine protein/creatinine ratio, endogenous creatinine clearance, and renal B-mode ultrasonography; and for normal systemic blood pressure with Doppler pressure cuff measurement. Subsequently, the cats were sedated with ketamine hydrochloride, and values for mean intrarenal (arcuate artery) resistance to blood flow were determined by duplex Doppler ultrasonography, and expressed as the Pourcelot resistive index, a ratio of systolic to diastolic flow commonly used in duplex Doppler sonography in human patients. After duplex Doppler sonographic examination, histological normalcy of the kidneys was verified by evaluation of ultrasound-guided percutaneous renal biopsy. Based on the obtained resistive indices, 95% confidence intervals for normal values were calculated as follows: left kidney, 0.52 to 0.60; right kidney, 0.55 to 0.63. No statistically significant difference was noted between the values obtained for the right versus the left kidney.