This invention relates to novel N-[[3-[3-Fluoro-4-(4-morpholinyl)phenyl]-2-oxo-5-oxazolidinyl]methyl]-ace- tamide derivatives, their acceptable acid addition salts, solvates and hydrates. The invention also provides compositions comprising a compound of this invention and the use of such compositions in methods of treating diseases and conditions beneficially treated by antimicrobial agents.