The iodinated cocaine analogue 2 beta-carbomethoxy-3 beta-(4-iodophenyl)tropane ([123I]beta-CIT), a new dopamine transporter, was preliminary tested in human brain. Two normal volunteers and two patients with Parkinson's disease were imaged with a high-resolution single-photon emission tomography scanner. The specific binding of [123I]beta-CIT in the basal ganglia and thalamus was high in normal volunteers. In addition, there was relatively intense uptake in the medial prefrontal area. Patients with Parkinson's disease who were older than controls showed significantly lower specific binding in the basal ganglia and thalamus and no uptake in the medial prefrontal cortex. This decrease in the dopamine transporter may be age related.