Purpose: The objective of the current study was to investigate the surface morphologic characteristics of prosthodontic composite materials treated with an acidulated phosphate fluoride (APF) agent. Materials and Methods: Seven composite materials (Artglass, Axis, Belleglass, Cesead II, Dentacolor, Solidex, and Targis) were examined. Each material was packed into a split plastic mold and was polymerized with a laboratory photo-curing unit. Half of each composite disk surface was coated with a varnish, and the entire surface of the sample was treated with an APF agent. After removal of the varnish, surface roughness values (Ra) for the treated and untreated (ie, previously varnish coated) sides of all specimens were recorded with a surface analyzer and observed with a scanning electron microscope. Results: Ra values for Cesead II, Solidex, and Targis showed a significant increase as a result of treatment with the APF solution. Microphotographs demonstrated that the macroinorganic fillers in the Cesead II and Solidex materials showed substantial dissolution caused by the APF agent. There were no significant statistical differences in the Ra values between the treated and untreated halves for any of the materials containing inorganic fillers composed entirely of diameters up to 1.0 µm. In particular, microphotographs of prepolymerized silica composite (classified as microfilled materials in Axis and Dentacolor) did not reveal any change of the specimen surfaces. Conclusion: The APF agent attacked inorganic fillers in the composite materials. Microfilled material surfaces were insensitive to the agent in comparison with macroinorganic filled material surfaces.