Availability of valid data is a prerequisite for medical data analysis. Traditional data collection (prospective studies, registries, use of administrative data) tends to be either expensive or inaccurate. By transferring the workflow of routine patient care to an electronic patient record(EPR), large amounts of detailed information are stored in a retrievable format, but the maintainance of EPRs in mainframe- or client/server-architecture is expensive.We therefore investigated the feasibility of an EPR based entirely on Web-Technology. The system is now operational since two years and has replaced the former paper-based patient records of the outpatient clinic completely (now 789 patients). With an average duration of access to all values of a specific laboratory day for a given patient taking 0.9s (SD:0.5s) and the automatic composition of a discharge letter taking 6.1s (SD:2.4s) the speed is adequate. We intend to enlarge the data pool by proliferating the system to other institutions.