Abstract: βCIT is labled with 131I by the peracetic acid method. 4 normal controls, 8 patients with PD and 3 patients with PS are studied by 131IβCIT SPECT imaging. Striatal specific uptake of 131IβCIT is calculated by the radioactivity ratio of striatal to cerebellar. The results show that the radiochemical purity of 131IβCIT is (97.6±0.3)%.131IβCIT remains stable for at least 4 h after incubated with waters and serum respectively. The striatal specific uptake of 131IβCIT in normal controls, PD and PS patients are (4.39±0.14)%,(2.95±0.68)% and (3.96±0.52)% at 4 h and (6.60±0.06)%,(3.85±0.71)% and (6.14±0.08)% at 20 h after administration. There is a significant reduction of striatial tracer uptake in PD patients compared to the controls and PS patients. Striatal specific uptake in contralateral to the clinical symptom side is more pronounced reduced than the ipsilateral side in PD patients. 131IβCIT uptake in PD patients is correlated with disease severity. These results suggest that 131IβCIT can be used for the diagnosis of Parkinsion's disease.