Self-microemulsifying drug delivery systems (SMEDDS) were developed to overcome the problems of delivery and administration of piroxicam, a drug with low bioavailability and gastrointestinal irritation, The in vitro properties of it were assessed. The solubility of piroxicam in several oils and surfactants was determined, and the compatibility of various oils and surfactants was investigated. Ternary phase diagrams were constructed to optimal area of microemulsion, and the influence of different oily phases, surfactants and co-surfactants was studied. The droplet size and dissolution of optimal formulation were determined to prove that the dosage form is a useful delivery system for piroxicam. In the optimized piroxicam SMEDDS, cinnamic alcohol was selected that gave the maximal solubility to piroxicam. Labrafil M 1944CS, Cremophor EL and Transcotol P were used as oils, surfactant and co-surfactant, respectively. Droplet size and distribution of three piroxicam SMEDDS formulations were (32.2 +/- 5.0), (40.1 +/- 6.4), (81.9 +/- 12.2) nm individually. And the releasing of piroxicam was rapid and complete. The optimized SMEDDS for piroxicam was obtained.