Objective: To explore whether the radioligand 2carboxymethoxy-3-(4-[123I] iodophenyl) tropane ([123I]CIT) and single-photon emission computed tomography (SPECT) can detect decreased striatal uptake in at-risk relatives of patients with Parkinson disease (PD). Patients and Methods: Ten PD patients, 10 at-risk first-degree relatives of PD patients, and 10 controls underwent [123I]-CIT and SPECT brain imaging. Their striatal uptake ratios were compared. Results: Age-adjusted specific to nonspecific striatal uptake ratios were lower in patients compared with controls and with relatives; however, ratios were similar in relatives and controls. Among relatives, ratios were consis-tently lower in subgroups postulated to be at higher risk for preclinical PD. Conclusion: Our findings provide preliminary support that [123I]β-CIT and SPECT may detect decreased striatal uptake in relatives of PD patients postulated to be at higher risk for PD.