OBJECTIVES:  Examine patient characteristics and predictors of pharmaceutical treatment class choice among US patients diagnosed with Parkinson’s Disease (PD). METHODS: This retrospective study utilized data from the MarketScan Claims and Encounters database over the period from 1/1/2006 through 12/31/2011.  Patients were included in the study if they were diagnosed with PD (with first such date identified as index date), were at least 35 years old, had continuous insurance coverage from 6 months prior through 12 months post index date, and received a post-period prescription a medication for one of the following anti-PD classes: dopamine agonist (DA), MAO-B inhibitor (MAO-B) or levodopa (LD).  The study consisted of descriptive analyses comparing the cohorts and logistic regressions examining predictors of medication class prescribed.   RESULTS: There were 4,916 individuals in the study (1,788 in DA cohort, 646 in MAO-B, and 2,482 in LD).  Results of the logistic regression revealed that older patients were significantly less likely to receive DA (OR=0.977; 95% CI 0.966-0.988) or a MAO-B (OR=0.968; 95% CI=0.954-0.983), compared to LD.  Compared to LD cohort, patients who receive a MAO-B were significantly less likely to be diagnosed with pre-period depression (OR=0.540; 95% CI 0.310-0.940) and patients who received a MAO-B or DA were significantly less likely to be diagnosed with psychoses (MAO-B - OR=0.220; 95% CI 0.105-0.459: DA – OR=0.732; 95% CI 0.542-0.989).  Furthermore, results revealed that patients diagnosed by a neurologist were significantly more likely to receive a DA (OR=1.651; 95% CI 1.353-2.014) or a MAO-B (OR=1.607; 95% CI 1.193 – 2.165), compared to LD.  Region of residence and health plan membership were also found to predict initial medication class.   CONCLUSIONS: These analyses indicate that patient characteristics, health status, diagnosing physician and access disparities all impact initial therapeutic class of medication prescribed for patients with PD.