The experiences obtained during the development of gas chromatographic and other (GC, TLC and infrared spectrophotometric) methods for the 7th edition of the Hungarian Pharmacopoeia for essential oils and drugs containing essential oils are summarized with emphasis on the selection of suitable internal standard for the gas chromatographic assays. The qualitative and quantitative estimation of bitter compounds and polyphenoles e.g. flavonoids and procyanidines by means of ultraviolet and infrared spectrophotometry and HPLC is also described. Some HPLC methods for the determination of anthocyan and carotinoid derivatives are also presented. These are not yet included in the pharmacopoeia but are successfully used for the analytical investigation of commercially available medicinal plants and drug products made thereof.