European exposure factor data have been collected in one centrally available, freely accessible site on the Internet: the ExpoFacts database (http://www.ktl.fi/expofacts/). The process of compiling the database required locating the exposure factor data and evaluating its general applicability and public availability. The scope of the ExpoFacts database covers 30 European countries, often each with its own approach for data generation and publication. The database includes information on food intake, time use, physiology, housing, and demographic parameters, as available. Information included in the database, as well as the challenges in collecting and compiling this information, are summarized. Data were found to be unavailable for ExpoFacts for a number of reasons: (1) data have not been collected, (2) collected data are not published, (3) the publishing format or language makes the data hard to locate and use, (4) copyright restrictions prevent presenting the data in an open access website, or (5) data exist, but are too expensive to acquire. Improving accessibility and harmonization of existing data would enhance the information base for exposure and risk assessments. In addition, the ExpoFacts project demonstrates a successful process for acquiring, storing, and sharing exposure factors data.