Purpose Paediatric solid cancers such as osteosarcoma, Ewing s sarcoma, rhabdomyosarcoma and neuroblastoma are the most common cancers in children besides leukemia. These cancers have a poor prognosis, are highly metastatic and often resistant to current therapeutic approaches. Viscum album L. (mistletoe) is one of the most widely used complementary cancer therapies in Germany but little is known about its actual effects on paediatric solid cancers. Approved Viscum album L. extracts (VAE) basically contain water soluble compounds of the plant (lectins, viscotoxins). However, mistletoe also contains triterpene acids (mainly oleanolicand betulinic acid) that are water-insoluble. The antitumorigenic properties of these solubilized triterpene acids are the subject of ongoing research. The aim of this study is to determine the effects of different VAE containing either lectins (viscum), triterpene acids (TT) or a combination thereof (viscum TT) on solid tumor models in vitro and in vivo.