The overall goal of this study is to evaluate the use of dopamine transporter (DAT) imaging as a diagnostic tool in subjects with early parkinsonian symptoms, in whom Parkinson's disease (PD) or parkinsonian syndrome (PS) is suspected, but the diagnosis remains unclear from a clinical standpoint.

• Subjects will be referred to the Institute for Neurodegenerative Disorders (IND) by practicing general neurologists with genuine uncertainty regarding the subject's diagnosis.
• Subjects with suspected PD or PS will be evaluated clinically and with DAT imaging, using b-CIT and SPECT. The DAT imaging procedure will take place over two days:
• On the first day participants are injected with [123I]ß CIT, an investigational radioactive material that localizes in the brain. Study participants will also have a thorough neurologic examination and standard neuropsychological testing, including testing of memory, concentration, abstraction and visual spatial functions.
• Twenty-four hours later study participants return to the Institute for Neurodegenerative Disorders where an investigational scanning procedure will be used to obtain SPECT (single photon emission computed tomography) images of the brain.
• Subjects will be asked to return within 3 months following the imaging study to have a repeat neurological examination by the two study neurologists at IND.
• Subjects will be asked to return at about 6 months and possibly again at one year following the imaging study for a final clinical evaluation by one of the study neurologists at IND.

Inclusion Criteria:

• Age >21
• Any parkinsonian or extrapyramidal symptoms
• Parkinsonian symptoms for < 2 years duration.
• No significant abnormalities on screening laboratory studies including: CBC, Chem-20 and urinalysis.
• Willingness to comply with study protocol.

Exclusion Criteria:

• Pregnancy
• Significant medical disease including abnormalities on screening biochemical or hematological labs or abnormal electrocardiogram (ECG).