A public resource, SIDER, has been developed to capture phenotypic effects of drugs. It connects 888 drugs to 1450 side effect terms, with information on frequency for one-third of the drug-side effect pairs. For 199 drugs, the side effect frequency of placebo administration could also be extracted. The resource is freely available for academic research at http://sideeffects.embl.de. Side effects are phenotypic responses of the human organism to drug treatment. They are an important source of human phenotypic information, but research on this topic has been hampered by insufficient accessibility of data. SIDER was developed to address this issue by compiling package inserts from public sources, particularly from the US Food and Drug Administration (FDA), in the form of Structured Product Labeling (SPL) or Portable Document Format (PDF) documents. Text mining was used to extract side effects from the differently formatted labels. The standardized Coding Symbols for a Thesaurus of Adverse Reaction Terms (COSTART) were used as the basic lexicon of side effects. Drug names were mapped to PubChem identifiers to facilitate linking to other databases. SIDER contains 62,269 drug-side effect pairs and covers 888 drugs and 1450 distinct side effects. 70% of drugs have between 10 and 100 different side effects. 55% of all side effects occur for <10 drugs. 33% of all side effects occur for 10–100 drugs; 12% of all side effects occur for >100 drugs. Labels for 79% of the drugs were available in SPL format, and 75% in PDF. 798 of these drugs are FDA-approved; the remaining 90 drugs have either been previously approved but were since withdrawn from the market or are marketed outside the United States. The resource was used to analyze how specific side effects are to drug classes. It was found that most side effects can occur for more than one drug class. Common side effects reveal important information as they can point to shared underlying mechanisms of action. The resource also provides frequency information for side effects, with exact frequencies for 23,631 drug-side effect pairs (38% of all pairs). Frequency information could be deduced for 6448 (27%) of all pairs with frequency information. The median frequency in patients of 'frequent' side effects occurring in >1% of patients is 5%. The resource is available for academic research and allows users to download the whole database and examine the side effects of individual drugs. It also provides a website where users can explore the package inserts through the concept of 'augmented browsing'. The database will be updated periodically with the incorporation of new drug labels. It is available under Creative Commons Attribution-Noncommercial-Share AA public resource, SIDER, has been developed to capture phenotypic effects of drugs. It connects 888 drugs to 1450 side effect terms, with information on frequency for one-third of the drug-side effect pairs. For 199 drugs, the side effect frequency of placebo administration could also be extracted. The resource is freely available for academic research at http://sideeffects.embl.de. Side effects are phenotypic responses of the human organism to drug treatment. They are an important source of human phenotypic information, but research on this topic has been hampered by insufficient accessibility of data. SIDER was developed to address this issue by compiling package inserts from public sources, particularly from the US Food and Drug Administration (FDA), in the form of Structured Product Labeling (SPL) or Portable Document Format (PDF) documents. Text mining was used to extract side effects from the differently formatted labels. The standardized Coding Symbols for a Thesaurus of Adverse Reaction Terms (COSTART) were used as the basic lexicon of side effects. Drug names were mapped to PubChem identifiers to facilitate linking to other databases. SIDER contains 62,269 drug-side effect pairs and covers 888 drugs and 1450 distinct side effects. 70% of drugs have between 10 and 100 different side effects. 55% of all side effects occur for <10 drugs. 33% of all side effects occur for 10–100 drugs; 12% of all side effects occur for >100 drugs. Labels for 79% of the drugs were available in SPL format, and 75% in PDF. 798 of these drugs are FDA-approved; the remaining 90 drugs have either been previously approved but were since withdrawn from the market or are marketed outside the United States. The resource was used to analyze how specific side effects are to drug classes. It was found that most side effects can occur for more than one drug class. Common side effects reveal important information as they can point to shared underlying mechanisms of action. The resource also provides frequency information for side effects, with exact frequencies for 23,631 drug-side effect pairs (38% of all pairs). Frequency information could be deduced for 6448 (27%) of all pairs with frequency information. The median frequency in patients of 'frequent' side effects occurring in >1% of patients is 5%. The resource is available for academic research and allows users to download the whole database and examine the side effects of individual drugs. It also provides a website where users can explore the package inserts through the concept of 'augmented browsing'. The database will be updated periodically with the incorporation of new drug labels. It is available under Creative Commons Attribution-Noncommercial-Share A