The monoamine transporter was studied in 4 healthy controls and 5 patients with early Parkinson's disease (PD), who had not received any antiparkinsonian medication, by means of positron emission tomography (PET) using two novel ligands, ["CIP-CIT and ["CIP-CFT. Both ligands showed highest uptake in the striatum. There was intermediate accumulation of activity in the thalamus and midbrain, which was more marked for ["CIP-CIT than for [llC]P-CFT. In the cortical areas, uptake of both ligands was not different from that seen in the cerebellum. In the controls, the putamento-cerebellum and caudate-to-cerebellum ratios for [l'C]P-CFT were higher than those for [llC]P-CIT (putamen: 3.15 5 0.39 for ["CIP-CFT, and 1.84 i 0.10 for ["CIP-CIT caudate: 3.15 ? 0.31 for [llC]P-CFT, and 1.95 ? 0.17 for [l'CIP-CIT). Reduction from mean control value in PD patients was greater for [WIP-CFT (45% in the putamen contralateral to the predominant symptoms, P < 0.001) than for [11Cl/3-CIT (20%, P > 0.05). ["CIP-CFT uptake in the caudate nucleus was also diminished in PD patients (to 80% of the control mean, P < 0.05), whereas [llC]p-CIT was within normal range (reduced to 90% of the control mean). These results indicate that both ["CIP-CIT and ["Clp-CFT are useful PET ligands to study brain monoamine transporter in healthy controls and in patients with PD. However, [WIP-CFT seems superior to [llC]P-CIT in this respect.