The present invention relates to 5-[[4-[2-(methyl-2-pyridinylamino)ethoxy]phenyl]methyl]-2,4-thiazolidinedione phosphate, a novel salt of rosiglitazone and to novel polymorphic forms thereof. The invention is also directed to processes for preparation of rosiglitazone phosphate and its polymorphs. The compounds of the invention are useful for treatment and/or prophylaxis of diabetes mellitus, conditions associated with diabetes mellitus and certain complications thereof.
