The large family of: Asteraceae yields a broad spectrum of biologically active metabolites. Many of these compounds are applicable in medicine, some of them, however, exhibit adverse effects and a health risk, especially in self-medication with medicinal plants. The article is concerned with the toxicity of caurane diterpenes, sesquiterpenic lactones, thujone, pyrrolizidine alkaloids and polyynes. The biological activity and its intensity is related to the chemical structure, the mechanism of the effect and the clinical manifestations of intoxications are described forty species of medicinal plants are included with their potential adverse effects on human and animal organisms.