OBJECTIVES:  To examine utilization of  Rasagiline and Selegiline, two commonly prescribed medications for the treatment of Parkinson's Disease (PD).   METHODS: Data for this study were obtained from the US i3 LabRx database over the time period from January 1, 2006 through December 30, 2010.  Patients were included in the analysis if they were prescribed Rasagiline or Selegiline (with first such date identified as the index date), were diagnosed with PD, and had continuous insurance coverage from 6 months prior through 12 months post index date.  Analyses are primarily descriptive in nature. RESULTS: There were 1242 individuals included in the study - 926 who initiated on Rasagiline and 316 who initiated on Selegiline.  Patients initiated on Rasagiline, compared to Selegiline, were significantly younger (63.2 years vs. 65.4 years; P=0.0020); less likely to have a gap in therapy for at least 60 days (0.86% v 2.85%; P=0.0088; associated with a higher medication possession ration (MPR) (0.62 vs. 0.52; P<0.0001); and associated with a longer persistence of use (259 days vs. 229 days; P=0.0013). Despite the fact that Selegiline is approved only as adjunctive use, there was no statistical significant difference in the percentage of patients using the medication in combination with another PD medication (75.96% vs. 73.43%; P=0.3783).  CONCLUSIONS: Results from this retrospective study indicate that the two medications are both used primarily as adjunctive medications.  Furthermore, approximately 25% of patients who initiate on Selegiline were found to not have used  other PD medications adjunctively in the 1 year post initiation.  Rasagiline use, compared to use of Selegiline, was found to be associated with fewer gaps in therapy, a higher MPR and longer persistence in therapy.