Abstract: AIMTo evaluate the similarity between two chromatographic fingerprints automatically with computer. METHODSChromatogram can be treated as vector of hyperspace, and the similarity between them can be counted according to vectorial angle formula. This process was performed with software written in Visual Basic 6.0. The two main functions of this software are automatic peak tracking in two fingerprints under the same analytic condition and computing the similarity automatically. RESULTSThe HPLC fingerprints of eleven kinds of Evodia rutaecarpa (Juss.) Benth (a traditional Chinese herb) from different sources were obtained and the similarities were calculated with this software. This method was shown to be a good way to evaluate the similarity between two fingerprints. A sample washed seven times with hot water can be clearly discriminated from other samples of Evodia rutaecarpa (Juss.) Benth with similar results. CONCLUSIONThis method is a good way to evaluate the similarity between two fingerprints and is helpful in quality control of traditional Chinese medicine.