ChemIDplus is a dictionary of over 400,000 chemicals (names, synonyms, and structures). ChemIDplus includes links to NLM and other databases and resources, including links to federal, state and international agencies. NLM makes a subset of ChemIDplus data available for download. The ChemIDplus Subset does not include the structure or the toxicity data available from the NLM web versions of the database. The ChemIDplus Subset is updated monthly.