This study evaluated the usefulness of thallium-201 muscle perfusion scan (Tl-201 muscle scan) to investigate perfusion reserve in the lower limbs of asymptomatic Type 2 diabetic patients without peripheral ischemia findings. Tl-201 muscle scan was carried out in 36 diabetic male patients with Type 2 diabetes mellitus of more than 10 years in duration who had no evidence of peripheral arterial disease in their history, physical examination, or Doppler ultrasonography. A control group consisted of 24 healthy age-matched nondiabetic men. Each subject flexed their right foot maximally both dorsally and plantar 60 times. In the middle of this exercise, 2mCi Tl-201 was injected intravenously. Three minutes after the injection, a posterior image of both calves was obtained using a gamma camera. Rectangular regions of interest (ROIs) were symmetrically drawn over both calves. The total count (Ct) in the resting calf was subtracted from the Ct in the exercising calf, and the percentage increase, termed the perfusion reserve, was determined. A significant difference was found between the perfusion reserves of the Type 2 diabetic patients and control groups (70.2+/-10.7% and 98.6+/-9.4%, respectively; P<.05). In conclusion, the perfusion reserve in the lower limb muscles in Type 2 diabetic patients may be measured by Tl-201 muscle perfusion scan.