Stearic acid nanoparticles were prepared in this study by melt-homogenization to investigate the possibility of them as a new kind of drug carrier system. Some physicochemical properties of stearic acid nanoparticles were studied and morphology examined by transmission electron microscope. Cyclosporin A as a model drug was then encapsulated into stearic acid nanoparticles. Following the establishment of high performance liquid chromatography assay for cyclosporin A analysis in stearic acid nanoparticles or blood samples, the encapsulation ratio of cyclosporin A to stearic acid nanoparticles was estimated and pharmacokinetics as well as bioavailability of cyclosporin A stearic acid nanoparticles after oral administration to Wistar rats were studied, using the Sandimmun Neoral