OBJECTIVES: Myasthenia Gravis (MG) is a rare neuromuscular disease affecting an individual’s voluntary muscular control.  It is estimated that the US prevalence of MG is 20/100,000, however there is little information specifically focused on older adults.  Evidence suggests that MG impacts men and women differently with women having an earlier onset of disease than men.  We calculated the prevalence of MG among Medicare beneficiaries and assessed differences in patient characteristics and costs between male and female patients. METHODS: To complete our study we used the Medicare LDS 5% sample including years 2011-2013.  MG patients were identified using the ICD-9 code 358.0 and were required to have at least two diagnoses.  MG patients were indexed in the year 2012 and followed for a period of one year to assess costs and healthcare utilization. RESULTS: We identified 2,047 MG, 1,050 male and 997 female, patients in the Medicare sample giving a prevalence of 77/100,000.  Male and female prevalences were 68 and 87/100,000, respectively.  On average, male patient were older than females by 2.66 years (p=0.01), had higher CCI scores (2.59 males, 2.21 for females, p=0.01) and were less likely to be receiving Medicare disability benefits (16.67% and 25.68%, p=0.01).  Female MG patients were more frequently in the highest category for inpatients stays (12.94%, 9.14%, p=0.03) and ER visits (36.81%, 31.81%, p=0.01). CONCLUSIONS: Among Medicare beneficiaries MG is more prevalent than in the US population.  Large differences seen in the literature between male and female patients were not seen, most likely due to the specific nature of the Medicare beneficiary population.  Female MG patients had higher rates of healthcare utilization, but cost differences were negligible.