Danazol, a steroid with very low aqueous solubility and poor bioavailability, and its coprecipitates were characterized for solubility, dissolution rate and bioavailability. Solubility diagrams of danazol in aqueous hydroxypropyl β-cyclodextrin (HPCD) solutions and isopropanol/water solutions were constructed with concentration of HPCD solutions ranging between 0.65 and 65.0 mM. Coprecipitates of danazol and HPCD at ratios ranging from 1:1 to 1:10 were prepared by solvent evaporation method using ethanol and by freeze drying method. Solubility diagrams indicated the existence of a complex between danazol and HPCD, and showed a remarkable increase in danazol solubility. Stability constants of the complex and thermodynamic parameters of complexation were calculated in both aqueous and aqueous/organic solvents; the presence of isopropanol appeared to have negative effect on the stability of the complex. Dissolution profiles of the coprecipitates demonstrated higher dissolution rates than pure danazol. Characterization of coprecipitates by DSC and X-ray diffraction techniques showed that danazol existed almost exclusively in crystalline form in coprecipitates at low danazol to HPCD ratios; while at high ratios, danazol appeared to exist in a non-crystalline form. No distinct differences in the product characteristics could be attributed to the method of preparation. Oral bioavailability of the coprecipitate (danazol: HPCD, 1:10) and a marketed danazol were tested in Wistar rats in a two-way, randomized cross-over study. The area under the curve (AUC) of plasma concentration versus time was significantly higher (P < 0.05) for the complex than the commercial formulation, with mean AUC value more than two-fold higher for the complex. The bioavailability of the coprecipitate relative to the commercial formulation was calculated to be 237%. The peak plasma concentration (C m a x ) of the coprecipitate was higher and the time to reach the peak (T m a x ) was lower for the complex. The greater rate and extent of absorption of danazol from the complex makes it a formulation with the potential to decrease the oral dose of danazol. Absolute bioavailability of the coprecipitate and commercial formulation was 14.2% and 6.2%, respectively.