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In this 12-week, open-label pilot study, the investigators will enroll 20 subjects with Parkinson's Disease to determine if two doses of Zonisamide are tolerable and demonstrate clinical benefit for Dyskinesias. The primary outcome measure is tolerability, as determined by number of subjects able to complete the study on their originally assigned dosage. Secondary outcome measures will use the Unified Dyskinesia Rating Scale (UDysRS), comprised of an Objective Section and a Historical Section, to compare baseline to 6 and 12-week measurements. Additional analysis of the effect of Zonisamide on quality of life will be measured by the Parkinson's Disease Quality of Life Questionnaire (PDQ-39).

Inclusion Criteria:

• Diagnosis of PD
• Identified dyskinesias of the limbs or trunk as agreed upon by subject and investigator, with dyskinesias considered moderately to completely disabling (UPDRS question 33, greater or equal to 2)
• Able to provide informed consent and swallow capsules
• Stable doses of dopaminergic therapy for 2 weeks before and expected throughout the study.

Exclusion Criteria:

• Atypical parkinsonism
• Concurrent use of amantadine or active DBS where patient has some control over settings
• Prior surgery for PD
• Sulfa allergy or intolerance of zonisamide
• Significant concomitant medical illness in the opinion of the Principal Investigator (renal disease, liver disease)
• Pregnant subject or a subject who plans to become pregnant