Inclusion complex of ibuprofen with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) in aqueous solution and in the solid state was evaluated by the solubility method and the instrumental analysis such as infrared spectroscopy, thermal analysis and x-ray diffractometry. The aqueous solubility of ibuprofen was increased linearly with the increase in the concentration of HP-β-CD, showing an A_L type phase solubility diagram. The results showed that the dissolution rate of ibuprofen was significantly increased by complexation with HP-β-CD. Ibuprofen-HP-β-CD complex enhanced the mean plasma concentration levels and the area under plasma concentration-time curve after oral administration compared to those of the drug alone. It is concluded that the complex of ibuprofen with HP-β-CD increases the dissolution rate and improves the bioavailability of the ibuprofen by the formation of a water-soluble complex.