Ibuprofen is one of the nonsteroidal anti-inflammatory drugs (NSAID) and has shown antiinflammatory; antipyretic, and analgesic activity in both animals and humans. But it causes gastric mucosal abnormalities including edema, erythema, and submucosal petechial hemorrhages and erosin in human. In addition, based on the pharmaceutical point of view the compression and dissolution ability of ibuprofen is known as poor. Therefore we studied to develop novel formulation containing water-insoluble drug, ibuprofen, using microemulsion consisting of surfactant, oil phase, and water phase was prepared for the purpose of increasing its bioavilability The physicochemical properties such as particle size, dissolution rate, solubility of ibuprofen in the system were determined. After oral administration of ibuprofen containing the microemulsion system, to Sprague-Dawley rats, pharmacokinetic parameters were also obtained. For the formulation in the study, oleic acid, linoleic acid, and several kinds of glycerides and triglycerides were used as an oil phase with several surfactants. Diethylene glycol monoethyl ether (Transcuto $l^{ }$) or saturated polyglycolized glycerides (Labrafil $^{ }$)as surfactant was used, the domain of microemulsion was wide. The diameter of o/w microemulsion was ranged from 90 to 220 nm. Microemulsion, prepared with unsatulated polyglycolized glycerides (Labrafil $^{ }$) and the 2 : 1 molar mixture of diethylene glycol monoethyl ether (Transcuto $l^{ }$)/polyoxyethylene(4) lauryl ether (Bri $j^{ }$ 30) , is expected to be promising system that increased the bioavilability of ibuprofen.ibuprofen.