Ligusticum chuanxiong Hort., a plant that is frequently used in traditional Chinese medicine, has been studied using HPLC-coupled spectroscopic techniques such as HPLC-UV, HPLC-MS as well as HPLC-NMR. With the aid of these modern spectroscopic techniques, the main constituents, namely senkyunolide A, butylphthalide, neocnidilide and Z-ligustilide, have been characterized and identified. Phthalide dimers, present in smaller amounts, have been identified by HPLC-UV and HPLC-MS analysis and compared with reference compounds. Stereochemical features of some phthalide monomers have been determined by detailed spectroscopic studies for the first time.