The paper deals with the evaluation of the content and quality of the essential oil of Melissa officinalis in various leaf insertions in the course of the ontogenetic development of the plant. The quality of the drug after the administration of the preparation Rastin 30 DKV in the form of granules was not changed in comparison with control samples. The experimental work, subsequent analysis of samples, and evaluation of results led to conclusions important from the viewpoint of significant changes in the content and composition of the essential oil taking place in the plant in the course of the vegetation period.

        Key words: Melissa officinalis – essential oil – neral – geranial – caryophyllen – ontogenesis