Background and Methods: Over the past 3 years, with support by the European Union within the 6th Framework Programme and by the pharmaceutical industry, the ESID Online Database has collected data from 7,047 patients with primary immunodeficiencies (PIDs) in 30 countries. The system is available via a standard internet browser for users in registered documenting centers with their personal login. It comprises a common core dataset for 212 PIDs and large disease-specific data models for 33 diseases. These can be used for international studies on these cohorts., Results: First analyses on the Therapy and Quality of Life section have shown that 42% of the registered living patients receive immunoglobulin replacement therapy. 76% of these receive intravenous immunoglobulins (IVIG), whereas 23% use the subcutaneous method of application (SCIG). In Germany, compared to the European figures, SCIG therapy is much more common, reaching 54%, whereas 46% of the patients receive IVIG. When analyzing the large cohort of patients with common variable immunodeficiency (CVID), patients on SCIG have less sick days and less days in hospital per year than those on IVIG., Conclusion: The acceptance of this new online system within Europe has been positive over the last few years and the database has now reached a state where it can be the basis for extensive international studies. However, with 551 patients, Germany only contributes 7.81% of the entered datasets. This is mainly due to a lack of time and manpower in the documenting centers and to time-consuming procedures for ethics approval.