PubChem, a key chemical information resource for the biomedical research community, has undergone significant improvements in recent years. New data content has been added, including spectral information, scientific articles mentioning chemicals, and information for food and agricultural chemicals. PubChem has also released new web interfaces, such as the PubChem Target View page, Sources page, Bioactivity dyad pages, and Patent View page. Additionally, a major update to PubChem Widgets and a new programmatic access interface, PUGView, have been introduced. PubChem organizes its data into three inter-linked databases: Substance, Compound, and BioAssay. The Substance database archives depositor-contributed descriptions of chemical substances. The Compound database stores unique chemical structures extracted from the Substance database through structure standardization. The BioAssay database contains the description and test results of biological assay experiments. As of August 2018, PubChem contains 247.3 million substance descriptions, 96.5 million unique chemical structures, and 237 million bioactivity test results from 1.25 million biological assays. The spectral information content in PubChem has substantially increased, with over 591,000 compounds having one or more types of spectral information available. PubChem has also integrated data from Springer Nature, providing over 26 million links between 600,000 chemical substances and four million papers. Additionally, annotations from authoritative sources for agricultural and food chemicals have been added to PubChem. PubChem has introduced a legacy designation for collections that are not regularly updated, helping users identify outdated records. Atomic mass values have been updated using the latest IUPAC recommendations. PubChem has also introduced a dynamic web traffic throttling approach to manage programmatic access requests and ensure service availability. New web interfaces include the PubChem Target View page, which provides a target-centric view of PubChem data for a given gene or protein. The Bioactivity dyad page presents bioactivity data for a given chemical tested in a particular assay or against a particular target. The Patent View page summarizes chemicals mentioned in a given patent, along with other information such as patent title, abstract, and classification. PubChem Widgets 2.0f allow users to display PubChem data on their own webpages. PUG-View enables users to programmatically access annotations presented on the Summary or Record page of PubChem records. PubChem has also introduced a dynamic traffic throttling system to help maximize uptime and request handling speed. PubChem continues to improve and develop tools and services that enable rapid access to information, including new efforts to enhance search and reorganize content with a focus towards summarizing what is known along with the evidence for assertions about the associations between biologically important entities. PubChem data, tools, and services are provided to the public free of charge.PubChem, a key chemical information resource for the biomedical research community, has undergone significant improvements in recent years. New data content has been added, including spectral information, scientific articles mentioning chemicals, and information for food and agricultural chemicals. PubChem has also released new web interfaces, such as the PubChem Target View page, Sources page, Bioactivity dyad pages, and Patent View page. Additionally, a major update to PubChem Widgets and a new programmatic access interface, PUGView, have been introduced. PubChem organizes its data into three inter-linked databases: Substance, Compound, and BioAssay. The Substance database archives depositor-contributed descriptions of chemical substances. The Compound database stores unique chemical structures extracted from the Substance database through structure standardization. The BioAssay database contains the description and test results of biological assay experiments. As of August 2018, PubChem contains 247.3 million substance descriptions, 96.5 million unique chemical structures, and 237 million bioactivity test results from 1.25 million biological assays. The spectral information content in PubChem has substantially increased, with over 591,000 compounds having one or more types of spectral information available. PubChem has also integrated data from Springer Nature, providing over 26 million links between 600,000 chemical substances and four million papers. Additionally, annotations from authoritative sources for agricultural and food chemicals have been added to PubChem. PubChem has introduced a legacy designation for collections that are not regularly updated, helping users identify outdated records. Atomic mass values have been updated using the latest IUPAC recommendations. PubChem has also introduced a dynamic web traffic throttling approach to manage programmatic access requests and ensure service availability. New web interfaces include the PubChem Target View page, which provides a target-centric view of PubChem data for a given gene or protein. The Bioactivity dyad page presents bioactivity data for a given chemical tested in a particular assay or against a particular target. The Patent View page summarizes chemicals mentioned in a given patent, along with other information such as patent title, abstract, and classification. PubChem Widgets 2.0f allow users to display PubChem data on their own webpages. PUG-View enables users to programmatically access annotations presented on the Summary or Record page of PubChem records. PubChem has also introduced a dynamic traffic throttling system to help maximize uptime and request handling speed. PubChem continues to improve and develop tools and services that enable rapid access to information, including new efforts to enhance search and reorganize content with a focus towards summarizing what is known along with the evidence for assertions about the associations between biologically important entities. PubChem data, tools, and services are provided to the public free of charge.