Solid forms of fesoterodine fumarate

13New solid forms of fesoterodine fumarate are described. In particular, amorphous fesoterodine fumarate, characterized by a powder X-ray diffraction spectrum as shown in FIG. and by an IR spectrum as shown in FIG. is described. Also fesoterodine fumarate in crystalline form I, characterized by a powder X-ray diffraction spectrum as shown in FIG. , by a DSC profile as shown in FIG. , by an IR spectrum as shown in FIG. , by a solid state C-NMR spectrum as shown in FIG. and by a Raman spectrum as shown in FIGS. and is described.