A process for the purification of an impure preparation containing hydrocodone by means of a reverse phase preparative chromatography process is provided. In an illustrative embodiment a chromatographic column is loaded with a stationary phase, typically a silica particle having an organic ligand bound thereto. The impure preparation is acidified and passed through the column with a loading ratio of from about 10 to about 1000. The column is eluted, typically with an aqueous solution of acetonitrile, and the purified hydrocodone is obtained in a specified fraction.