The main neuropathological feature in Parkinson's disease (PD) is a severe degeneration of the dopaminergic neurons in the substantia nigra resulting in a loss of dopamine in the striatum. Recently, a new radioligand (beta-CIT) for single photon emission computed tomography (SPECT) became available for in vivo imaging of the dopamine transporter on nerve endings of dopaminergic neurons in the striatum. The present results demonstrate that [123I]-beta-CIT SPECT allows a discrimination between early and late PD patients. In our opinion, these preliminary data suggest that [123I]-beta-CIT SPECT should be used from now on in longitudinal studies (such as the DATATOP study) in which the effects of (putative) neuroprotective interventions in PD are monitored.