Abstract: A polymorphic form of 5-[4-[2-(N-methyl-N-(2-pyridyl)amino)ethoxy]benzyl]-thiazolidine-2, 4-dione, maleic acid salt (the “Polymorph”) characterized in that it provides: (i) an infra red spectrum containing peaks at 1763, 912, 856 and 709 cm−1; and/or (ii) a Raman spectrum containing peaks at 1762, 1284, 912 and 888 cm−1; and/or (iii) a solid-state 13C nuclear magnetic resonance spectrum containing peaks at 111.0, 113.6, 119.8, 129.1, 130.9, 131.8, 134.7, 146.5, 152.7, 157.5, 169.5, 171.0, 178.7 ppm; and/or (v) an X-ray powder diffraction (XRPD) pattern which gives calculated lattice spacings at 5.87, 5.30, 4.69, 4.09, 3.88, 3.61, 3.53 and 3.46 Angstroms; a process for preparing such a compound, a pharmaceutical composition containing such a compound and the use of such a compound in medicine.