Abstract: AIM: To investigate the possibility of SA-NP (stearic acid nanoparticles) as a new kind of drug carrier. METHODS: SA-NP was prepared by melt-homogenization. Some of its physicochemical properties were investigated. Its morphology was examined by transmission electron microscope. Cyclosporin A (CyA), as a model drug was then encapsulated into SA-NP (CyA-SA-NP). Following the establishment of HPLC method for CyA in CyA-SA-NP or blood samples, the encapsulation ratio of CyA to SA-NP was estimated, and pharmacokinetics as well as bioavailability of CyA-SA-NP after po administration to Wistar rats were studied, using Sandimmun Neoral (an available microemulsion system of CyA) as a control. RESULTS: The mean diameter of CyA-SA-NP was 316.1 nm, while the encapsulation ratio of CyA to SA-NP reached to 88.36%. It was demonstrated by IR spectra and differential scanning calorimetry that no chemical reaction occurred between the CyA and SA. The relative bioavailability of CyA-SA-NP over control was nearly 80%, and the time to reach maximum concentration (T_max) of CYA after po administration of CYA-SA-NP was significantly delayed than the control, suggesting an obvious sustained release effect. CONCLUSION: SA-NP might be a very potential drug carrier.