The greater celandine (Chelidonium majus L.) is a species of the Papaveraceae family. The principal secondary metabolites of the plant are isoquinoline alkaloids; more than 30 were found here. The richest organ is the root, the total content of alkaloids in it reaching 2-3%. The dominant alkaloids of the root are chelidonine and coptisine. The aerial parts contain about 0.5-1.5% alkaloids. The principal base for the whole period of vegetation is coptisine, the representation of other alkaloids substantially changing during the development of the plant. Of nonalkaloidal secondary metabolites, esters of caffeic acid have recently been demonstrated in the plant drug. In the past, the drug was used to treat tumours. At present, the extract of alkaloids from the plant is the base of the preparation Ukrain showing immunomodulating activity and being employed in the therapy of different types of carcinomata. Chelidonium majus is also a component of some preparations employed in the diseases of the biliary tract and liver. Biological effect of the principal constituents of the drug are different and often quite antagonistic. As their representation varies in the course of vegetation, the efficacy of the summary preparations changes in dependence on the prevailing substance in the preparation.