Herbal medications are becoming increasingly popular with the impression that they cause fewer side effects in comparison with synthetic drugs; however, they may considerably contribute to acute or chronic poisoning incidents. Poison centers receive more than 100000 patients exposed to toxic plants. Most of these cases are inconsiderable toxicities involving pediatric ingestions of medicinal plants in low quantity. In most cases of serious poisonings, patients are adults who have either mistakenly consumed a poisonous plant as edible or ingested the plant regarding to its medicinal properties for therapy or toxic properties for illegal aims.In this article, we review the main human toxic plants causing mortality or the ones which account for emergency medical visits. Articles addressing "plant poisoning" in online databases were listed in order to establish the already reported human toxic cases.The current review introduces herbal plants toxicity and herb-drug interactions to warn the health professionals about possible consequences of unconscious uses of medicinal plants. The reported cases extracted from our prepared database were classified on the basis of the main toxic effects of plants, and the most prominent constituents of the plants which are responsible for specific toxic effects.Considering the long history of consumption of herbal medicines in different societies, people may wrongly think that medicinal plants are fully harmless and nontoxic. Prescription, preparation and consumption regulations of medicinal plants are not clear and strict as well as their marketing regulations that differ from country to country. The extensive and various consumption of medicinal plants without adequate observation is the most important reason for poisoning by medicinal plants.