Muscle blood flows by means of hydrogen gas clearance method were measured on hindlimb muscles in sedentary control (nE) and exercised (Ex) spontaneously hypertensive rats (SHR) . SHR and Wistar control rats (WCR) were divided into two groups at 7 weeks of age ; SHRnE, SHREx and WCRnE, WCREx. Exercised rats were bred in cages with rotating wheels capable of running voluntarily for additional 10 weeks. Body weights of exercised groups in both SHR and WCR were lower than those of sedentary controls, whereas food consumptions of exercised rats tended to be more than those of sedentary controls. Ratios of the heart weight to the body weight of SHR and WCR were higher in exercised groups. There was no significant difference in systolic blood pressure obtained by an indirect tail-cuff method between exercised and sedentary control SHR. Resting blood flows in both M. Gastrocnemius and M. Soleus showed lower values in SHR groups than those in WCR groups. Postexercise blood flows at 1 Hz and 5 Hz were higher in exercised groups. These results suggest that peripheral adaptability of blood flow control to the exercise is still normal on hindlimb muscles in SHR.