Starch acetates (SA) have been investigated as novel, multifunctional excipients for the direct compression tableting process. In this study, the ®lm-forming ability of SA (DS 2.8) and the effect of commonly used plasticizers on the physical properties of SA ®lms were evaluated. The results were compared with the properties of ethylcellulose (EC). Free ®lms were prepared by a solvent-cast method. Mechanical studies, water vapor and drug permeability tests, and thermal analysis (DSC) were used to characterize the ®lm-forming ability of SA and ef®ciency of tested plasticizers. SA ®lms were tougher and stronger than EC ®lms at the same plasticizer concentration. Also, in most cases, the water vapor permeability of SA ®lms was lower than that of EC ®lms. DSC thermograms supported the ®ndings of the tensile test: plasticizers with several small ester groups (e.g., triacetin and triethyl citrate) were the most compatible with SA. Due to the good mechanical properties, low water vapor, and drug permeabilities of the ®lms, SA seems to be a promising ®lm-former for pharmaceutical coatings. The toughness of SA ®lms may result from their dense ®lm structure, which is due to strong interaction forces between adjacent SA molecular chains.