Novel polymorph form III of Aprepitant and a method for preparation of novel form III is disclosed. New processes for the preparation of Aprepitant form II are disclosed. The processes involve transformation of form III to form II by heating in decalin and the precipitation of form II from a solvent or solvent mixture by cooling and/or addition of addition of seed crystals or an anti solvent. Solid dispersions containing Aprepitant form II in a suitable carrier are disclosed. A process for the preparation of the solid dispersion by evaporation of a solution of Aprepitant and the carrier in a suitable solvent is disclosed. Stable Aprepitant form II is disclosed. Further pharmaceutical compositions containing Aprepitant form II, III or solid dispersions containing Aprepitant form II in a suitable carrier are disclosed. A methanol solvate of Aprepitant is disclosed.