Voucher specimens and herbarium collections provide the foundation for many aspects of research in the plant sciences. Available for study and verification by contemporary and future workers, voucher specimens promote reproducibility in scientific method because permanent records document identification, distribution, and interspecific and intraspecific variation of species. The utility and importance of voucher specimens and herbarium collections in supporting research in weed science are discussed, and the collection, preparation, documentation, storage, and shipment of voucher specimens are detailed.