To determine if linezolid is superior to vancomycin in the treatment of nosocomial (acquired in the hospital) pneumonia due to MRSA in adult subjects. Subjects entered in to the study will have proven healthcare-associated methicillin-resistant Staphylococcus aureus pneumonia which will be treated with either linezolid or vancomycin.

• Drug: linezolid
• Drug: vancomycin

• Experimental: Subjects receiving linezolid for the treatment phase of the study
• Active Comparator: Subjects receiving vancomycin for the treatment phase of the study

Inclusion Criteria:

• Hospitalized male and female subjects with clinically documented nosocomial pneumonia proven to be due to methicillin-resistant staphylococcus aureus.
• Chest X-ray at baseline/screen or within 48 hours of treatment consistent with the diagnosis of pneumonia.
• Suitable sputum specimen defined as having less than 10 squamous epithelial cells and greater or equal 25 leukocytes or have a culture taken by an invasive technique within 24 hours of study entry.

Exclusion Criteria:

• Subjects who were treated with a previous antibiotic with MRSA activity (other than linezolid or vancomycin) for more than 48 hours, unless documented to be a treatment failure (72 hours of treatment and not responding).
• Subjects with severe neutropenia (<500 cells/mm3)
• Subjects with hypersensitivity to oxazolidinones or vancomycin.