Physicochemical properties of coprecipitate of chloramphenicol(CP)-polyvinylpyrolidone (PVP) and CP-hydroxypropylcellulose (HPC) were investigated. The dissolution rate and apparent solubility of CP from the coprecipitate increased the CP-PVP system, but the increase of apparent solubility was not significant in the CP-HPC system. IR spectral changes due to the possible formation of H bonds were observed in the coprecipitate of the CP-PVP system, but not in that of CP-HPC system. The CP in the coprecipitate was found to be an amorphous form by the differential scanning calorimetry and X-ray diffraction measurement. In the CP-PVP system, difference in properties between the coprecipitate and physical mixture was always found when the mixing ratio (wt.wt) of CP: PVP was < 7:3. The absorption of CP after oral administration of the coprecipitate powder and pellet in the dog was 1.2-1.9 times greater in area under plasma level-time curve (0-9 h) than that of the mixture.