Crystalline form of linezolid

A process for preparation of linezolid form III, characterized by peaks in the powder x-ray diffraction spectrum having 2θ angle positions at about 7.6, 9.6, 13.6, 14.9, 18.2, 18.9, 21.2, 22.3, 25.6, 26.9, 27.9 and 29.9 degrees, which comprises the steps of:

• (a) acetylating (S)—N-[[3[3-fluoro-4[4-morpholinyl]phenyl]-2-oxo-5-oxazolidinyl]methyl]amine of formula
• in a solvent optionally in the presence of an organic base to form linezolid;
• b) optionally seeding the reaction mixture formed in step (a);
• and
• c) isolating linezolid form III from the reaction mixture of (a) or (b);
• wherein the solvent is selected from the group consisting of ethylacetate, methylacetate, propylacetate, isopropylacetate, butylacetate, toluene and xylene.