There are conflicting reports regarding the action of streptozotocin (STZ) on blood pressure (BP) in rats. This study investigated the BP, metabolic and hormonal effects of increasing doses of STZ in Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR), with consideration to methodological aspects. Indirect tail-cuff systolic BP measured in a conscious state was mildly elevated after 2 to 4 weeks and remained so in severely diabetic, emaciated WKY, whereas there were no changes in the SHR. Four and 20 weeks after STZ administration, systolic, mean and diastolic BPs measured in a conscious state with an arterial catheter were unchanged in the diabetic WKY and were decreased in the diabetic SHR. Thus, the changes in BP depended on the method used. Dose-dependent increases in blood glucose were similarly evident under conscious and ether-anesthetized conditions. Triglycerides were increased, and blood insulin and thyroxine levels were decreased in both strains. Between-strain comparisons revealed that the hypoinsulinemic response was similar, but the hyperglycemic and hypertriglyceridemic responses were greater in the SHR. The findings provide a data base for further investigation on STZ diabetes. In addition, the results suggest a different BP and metabolic susceptivity to STZ treatment in the SHR and WKY.