Thallium-201 chloride (201Tl) kinetics, may be affected by serum insulin levels like potassium kinetics. The purpose of the present study was to use glucose and insulin to improve 201Tl accumulation in the tumor. The results showed that the tumor-to-normal tissue ratio after simultaneous injection of 201Tl, glucose and insulin was significantly higher than that after the injection of only 201Tl, and that a ring appearance seemed to occur after glucose and insulin injection. This preliminary study suggests that 201Tl accumulation in the tumor is enhanced by glucose and insulin administration.