Abstract: Production of tablets in pharmaceutical industry often is required to mixture the active ingredient (drug) with an inert material. Starch is shown as a good alternative material to be used as excipient. Thus, in this investigation the techniques: thermogravimetry and derivative thermogravimetry (TG/DTG), differential scanning calorimetry (DSC as well as thermomicroscopy were performed with aim to verify existence of interactions between aceclofenac (2-[2-[2-[(2,6-dichlorophenyl)amino]phenyl]acetyl]oxalacetic) with regular maize starch and waxy maize starch. Binary and physical mixtures of aceclofenac and starch in ratios 2:1, 1:1 and 1:2 (drug:starch) studied by the instrumental techniques showed that no interactions occurs between the drug and starches in any ratio, being maintained the properties of aceclofenac.