The objective of this study was to explore the principles of SUPAC-SS and its regulatory application in handling postapproval changes to nonsterile semisolid dosage forms. The types of postapproval changes that SUPAC-SS described were modifications in formulation (components and composition), batch size, manufacturing equipment & process, and the site of manufacturing. SUPAC-SS defined the levels of postapproval changes and what chemistry, manufacturing, and control tests should be conducted for each change level. The guidance also specified several occasions the manufacturers should perform in vitro release test (Franz cell diffusion test) and/or in vivo bioequivalence test. Finally, SUPAC-SS classified appropriate filing forms to be used in supporting postapproval changes. It was crystal clear that SUPAC-SS helped maintain the safety and quality of approved semisolid dosage forms when they were subject to certain postapproval changes. The availability of SUPAC-SS made contributions to reducing regulatory burdens of the industry, as well as expediting the postapproval process of regulatory agencies. This study also shed light on the background of relevant pharmaceutical sciences that the SUPAC-SS guidance adopted. Finally, the KFDA and the industry were strongly urged to implant a similar guidance in handling postapproval changes to semisolid dosage forms available in the Korean marketplace.