Traditional or alternative or complementary systems of medicine are popular not only in developing but also in developed countries. The assessment should take into account a description of herbal medicine in the medical or pharmaceutical literature or similar sources, or a documentation of knowledge on the application of such medicines without a clearly defined time limitation. Herbs, herbal materials, herbal preparations, traditional use of herbal medicines, and therapeutic activity are discussed. Active ingredients refer to ingredients of herbal medicines with therapeutic activity. Assessment of quality discusses pharmaceutical assessment. This should cover all the important aspects of the quality assessment of herbal medicines sufficient to make reference to a pharmacopoeial monograph. Preclinical toxicological studies can be undertaken to study safety of herbal medicines. In addition, side-effects may be documented according to normal pharmacovigilance practices. Acute toxicity test explains that if necessary, a histopathological examination should be conducted on organs or tissues showing macroscopic changes at autopsy. Local toxicity test is explained. This is a sensitization test for dermatological preparations. Herbal medicines are currently being used either as first line of medical care or in conjunction with conventional treatment. The principles of the clinical trials of herbal medicines are similar to those applied to synthetic drugs.