We included all Cochrane reviews of CHM. Protocols and reviews which have been withdrawn from publication were excluded. We defined CHM as preparations derived from plants or parts of plants (e.g. leaves, stems, buds, flowers, roots or tubers) that grow in China and have been widely used for medical purpose. CHM include single herbs (or extracts from single herbs) and compound formulas of several herbs in all forms of preparation formulation (e.g. oral liquid, tablet, capsule, pill, powder, plaster or injection liquid). It should be noted that our definition of CHM does not include plant-derived chemicals or synthetic chemicals which contain constituents of plants. For example, although Huperzia serrata has its origin in China, according to our definition, Huperzine A does not belong to CHM because it is a kind of alkaloid extracted from Huperzia serrata. In addition, we only included reviews discussing herbs which originated from China, reviews on herbs such as Passiflora and Echinacea, both of American origin, were invariably excluded.