Hot-melt extruded tablets with enteric and sustained-release properties were prepared using ketoprofen as a model drug and Eudragit L100 as the carrier. Ketoprofen, with a similar solubility parameter to Eudragit L100, was homogeneously dispersed in the polymer matrix in a non-crystalline state, and was identified by differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy analysis. To compare the enteric and sustained-release characteristics, tablets of physical mixtures and comminuted extrudates were also produced with a tensile strength of 5.0 kg/cm2. The drug release percentage was below 3% in 0.1 M HCl and a sustained release for 6 to 12 hours was obtained with the tablets prepared by direct cutting of the extrudates and by compressing the pulverized extrudates, while no enteric and sustained-release properties were exhibited by the physical mixture tablets. The release mechanisms of the two types of tablets from their extrudates were different only because of their porosity. For the cut tablets, the drug was released according to the erosion mechanism, whereas in the extruded tablets the release property was controlled by erosion and diffusion mechanisms simultaneously.