OBJECTIVES: Pneumonia is a major cause of mortality in the United States. The burden of methicillin-resistant and susceptible Staphylococcus aureus pneumonia (MRSAP and MSSAP) is unknown. The purpose of this study was to provide national estimates of MRSAP and MSSAP, identify trends and predictors of in-hospital mortality and hospital length of stay (LOS). METHODS: This was a retrospective analysis of the National Inpatient Sample from 2009 to 2012. Adult patients (age ≥ 18 years) with an ICD-9-CM primary diagnosis code for MRSAP (482.42) or MSSAP (482.41) were included. Data were weighted to generate national estimates. MRSAP and MSSAP incidence were reported as MRSAP and MSSAP discharges per 100,000 discharges. In-hospital mortality rates and hospital LOS were presented descriptively. Patient and hospital factors associated with mortality and LOS were identified using multivariate logistic and linear regression models. RESULTS: A total of 104,644 patients had a primary diagnoses of pneumonia due to S. aureus, 81,330 were due to MRSA. Most patients were over 65 years of age (63%) and predominantly white (65%). MRSAP incidence decreased steadily from 2009 (75 MRSAP/100,000 discharges) to 2012 (57/100,000) with no change in MSSAP. Mortality rates for MRSAP decreased from 2009 (6 MRSAP deaths/100,000 discharges) to 2012 (3.6/100,000) with no decline in MSSAP patients. Median length stay was higher for MRSAP (7.8 days) compared to MSSAP (6.1 days) and remained steady. Factors associated with an increased risk of in-hospital mortality included methicillin-resistance (OR 1.16), age ≥40 years (OR 3.3), ≥65 years (OR 8.46), and increased comorbid burden (OR 1.03). Occurrence of MRSA was associated with a longer length of stay. CONCLUSIONS: The incidence of MRSAP decreased among hospitalized adults in the US in recent years, with improvement in mortality but not in LOS. Though MRSA pneumonia is on the decline, national vigilance is still warranted to continue this trend.