In addition to discovery and development of single chemical entities into drugs, NIH also supports studies to determine the therapeutic potential of natural products that are usually prepared as complex mixtures ["complex natural products"]. For studies of complex natural products, the experts who serve on NIH peer review committees must be convinced that the natural products to be used in any study are described in sufficient detail that the results can be understood and independently reproduced. Whether or not the test material derives from American or foreign commercial companies or other sources, including individually prepared, unique mixtures, evidence must be provided that the source of the test material has been reliably identified. For botanical natural products, this evidence may include, but is not limited to, the correct plant name (Latin binomial with authority, cultivar where appropriate), geographic source of the material, time of harvest, plant part, and credentials of the person who collected and/or identified the material. The content of the test material should be described by the commercial company or tested by an independent laboratory. This should be accomplished through an analytical characterization of the major identified components, and, if known, the active component(s), in the product. Independent of the study design, verification of the samples before the start and at the end of the study is needed to ensure product stability. Additional quality control measures may include plans for archiving samples, batch to batch reproducibility studies, short term and long term stability, analysis of contamination with heavy metals and organic or inorganic inert or active components.