In dogs, diabetes mellitus and hyperadrenocorticism are causes of hypertension associated with increases in vascular peripheral resistance. In human patients, the renal resistive index (ri) and pulsatility index (pi) are related to hypertension and diabetes and are used as indicators of disease severity. In this study the renal vascular resistance was measured in 12 dogs with hyperadrenocorticism, three with diabetes mellitus and four with both conditions, and the possible relationships between the two indices, blood pressure and biochemical parameters were investigated. Hypertension, defined as a systolic blood pressure more than 150 mmHg, was recorded in two of the dogs with hyperadrenocorticism and three of the dogs with hyperadrenocorticism and diabetes. The overall mean values for RI, PI and systolic blood pressure were higher in the diseased group of dogs than in 27 healthy dogs, and both indices were correlated with blood glucose concentration.