Plants are the primary source of medicine for most of the world. The most fundamental step in the scientific study of medicinal plants is establishing their botanical identity. Many studies lack voucher specimens, which serve as permanent records of scientific investigations. This omission makes positive identification impossible and hinders reproducibility. Even when vouchers are cited, scientific names are often mishandled. A random survey of titles and abstracts of 100 publications revealed 20 with taxonomic errors. Mistakes included a lack of author citations, misspellings, and use of older synonyms instead of currently accepted names. A seemingly minor orthographic error makes it impossible to search electronic databases for information about a species. Medicinal plant manuscripts and National Institutes of Health proposals commonly lack scientific rigor in dealing with botanical names and documentation. This article examines common taxonomic problems relevant to medicinal plant research and provides a basic guide to plant taxonomy for medicinal plant researchers. Voucher specimens and their preparation, plant identification, and botanical nomenclature are discussed. References and other resources to assist investigators are cited.