Introduction: Asari radix et rhizoma (Xixin, Manchurian Wildginger, Asarum spp) is a herbal drug commonly used as an ingredient in traditional Chinese medicine (TCM). Many species of Asarum contain safrole and methyleugenol as the main components of their volatile oils. However, toxicological studies have shown that safrole and methyleugenol may be a hepatocarcinogen and/or genotoxic leading to concerns regarding the habitual consumption of this herbal drug. Materials and Methods: An HPLC method was established to assess the levels of safrole and methyleugenol in five batches of Asari radix et rhizoma and two TCM formulae containing this herbal drug as an ingredient. Analyses showed that the content of safrole in the dried herbal drugs tested ranged from 0.14–2.78 mg/ g whilst the content of methyleugenol ranged from 1.94–16.04 mg/g. Results: The present study demonstrated that following a 1-hour decoction, the amount of safrole was decreased by more than 92% resulting in the equivalent of no more than 0.20 mg/g safrole remaining in the aqueous extract. Similarly, the content of methyleugenol was decreased to the equivalent of 0.30–2.70 mg/g. Furthermore, both TCM formulae, after decoction, showed negligible amounts of safrole (maximum, the equivalent of 0.06 mg/ g), and only 1.38–2.71 mg/g of methyleugenol. Conclu-sions: The present study shows that a decoction procedure, similar to that traditionally used for Chinese herbal preparations, is able to effectively reduce the amount of safrole and methyleugenol effectively. Such a reduction in the content of safrole should be acceptable for therapeutic use.