A review.Arnica preparations are used externally for hematomes, contusions, sprains, rheumatic conditions, superficial inflammations of the skin and for local inflammations in the mouth.In this article botanical aspects of the two officinal Arnica species, A. montana and A. chamissonis, and their constituents are reviewed with 51 references.The pharmacol. effects of the individual constituents are discussed.An overview is given of the use of arnica preparations, their toxicity and adverse effects as well as of different phytomedicines with arnica available on the market in the Netherlands.Also an overview of the arnica-containing preparations that are used in homoeopathy is provided.As a conclusion it is stated that there is an extensive knowledge of the pharmacol. properties of the constituents of Arnica species, but that the efficacy of arnica preparations, however, has not yet been demonstrated by clin. research.Despite this, the value of Arnica species as a medicinal plant seems beyond doubt.