High performance liquid chromatography (HPLC) is a method used to determine inorganic and organic substances in biological samples. Nevertheless, many analytes cannot be detected using HPLC method, because they do not contain a necessary chromophoric or fluophoric groups. Derivatization is the solution of this problem. This process can be defined as a conversion of analyte to corresponding derivative which possesses in its structure a moiety compatible with suitable detector [1, 2]. Reagent responsible for conversion of analyte to a derivative needs to meet a lot of requirements. It needs to be selective e.g. to react only with analysed substances and it should not generate by-products. The derivatization reagent should react rapidly, quantitatively, at lowest possible temperature and weakly pH, and the excess of reagent should be easily removable from reaction medium [1, 3, 5]. The derivatization can be carried out in pre-column, post-column and on-column mode. In the pre-column derivatization, analytes are derivatized before injection on HPLC system, and the reaction products are separated and detected. In the post-column derivatization, the reaction is performed automatically by adding the derivatization reagent after separation but before detection. The third method is based on reaction, which simultaneously proceeds with column separation [2, 3, 5, 6]. The derivatization processes in gas and liquid chromatography are subject matter among researcher from all over the world. The Polish literature has only few review articles on derivatization process in liquid chromatography [2, 4, 55]. The present article reviews derivatization techniques used in HPLC. Derivatization techniques used in gas chromatography are classified due to the chemical nature of derivatization reagent [3, 56]. Our attention is focused on the analyte and derivatization reagent, which can be react with various functional groups such as amino, sulfhydryl, hydroxyl or carboxyl groups, occurring in the examined molecules. By chemically modification compounds into derivatives, they obtain necessary properties for chromatographic separation and accurate analysis.