Herbal medicines are being increasingly used for treatment of variety of disorders. Herbal medicines are generally thought to lack severe side effects. Despite of the general belief, herbal medicines are known to cause serious side effects and toxicities. On the other hand, physicians’ knowledge of herbal medicines and their potential toxicities are generally limited. Neurotoxicity, cardiac toxicity, pulmonary toxicity, hepatotoxicity, and nephrotoxicity are potential severe complications of herbal medicines. The subject of severe herbal medicine complications is reviewed.