The slightly water-soluble drug prazosin hydrochloride (PRH) and its inclusion with either β-cyclodextrin (βCD) or hydroxypropyl-β-cyclodextrin (HPβCD) were investigated. The phase solubility profiles of PRH with βCD and HPβCD were classified as B s - and A L -types, respectively. Stability constants with 1:1 molar ratio were calculated from the phase solubility diagrams and the solubility of PRH could be enhanced by 27.6% for βCD and 226.4% for HPβCD, respectively. Binary systems of PRH with βCD or HPβCD prepared by various methods were characterized by differential scanning calorimetry and Fourier transformation-infrared spectroscopy. It could be concluded that PRH could form inclusion complex with either βCD or HPβCD. The dissolution profiles of inclusion complexes were determined and compared with those of PRH alone and their physical mixtures. The dissolution rate of PRH was increased by βCD and HPβCD inclusion complexation remarkably. Both the preparation technique and nature of the carriers played important roles in the dissolution performance of the systems. All the systems with HPβCD showed better performance than the corresponding ones with βCD.