Online databases containing high throughput screening and other property data continue to proliferate in number. Many pharmaceutical chemists will have used databases such as PubChem, ChemSpider, DrugBank, BindingDB and many others. This work will report on the potential value of these databases for providing data to be used to repurpose drugs using cheminformatics-based approaches (e.g. docking, ligand-based machine learning methods). This work will also discuss the potentially related applications of the Open PHACTS project, a European Union Innovative Medicines Initiative project, that is utilizing semantic web based approaches to integrate large scale chemical and biological data in new ways. We will report on how compound and data quality should be taken into account when utilizing data from online databases and how their careful curation can provide high quality data that can be used to underpin the delivery of molecular models that can in turn identify new uses for old drugs.