Natural rubber latex proteins are a well-recognized cause of type-I allergic reactions that increasingly afflict health-care workers, housekeeping personnel, and other persons using latex gloves or latex products. More than a dozen individual latex allergens have been identified of which eight have received an international nomenclature designation. To study the biochemical and immunological properties in detail, it is desirable to clone and express each of these allergens. Proteins that are involved in rubber synthesis are most likely confined to latex whereas other enzymes, such as chitinases or glucanases, are also present in fruits and may account for the symptoms observed in the latex-fruit syndrome. The available data on the molecular characterization of latex allergens presented here illustrate the importance of this research in the production of better diagnostic tests and, perhaps, tools for immunotherapy.