Herbal remedies can result in indirect health risks when they delay or replace a more effective form of conventional treatment or when they compromise the efficacy of conventional medicines. Herbal remedies can also be associated with direct health risks. Long-standing traditional experience may tell much about striking and predictable symptoms of acute toxicity but it is a less reliable tool for the detection of reactions which are inconspicuous, develop gradually or have a prolonged latency period, or which occur uncommonly. Another reason why safety claims cannot always be based on traditional empiricism is that not all herbal remedies are firmly rooted in traditional medicine. The risk of a herbal remedy producing an adverse reaction depends not only on the remedy and its dosage but also on consumer-related parameters, such as age, genetics, concomitant diseases and concurrent use of other drugs. Another important determinant of the toxicity of herbal remedies is their quality. What is already known about the risks of herbal remedies must be systematically collected, disseminated and acted upon. What is yet unknown must be found out by herbal postmarketing surveillance and experimental research.