Primary immunodeficiencies (IDs) are caused by inherited genetic defects leading to intrinsic defects in cells of the immune systems. Most IDs are rare diseases and can be difficult to diagnose because similar symptoms characterize several disorders. Mutation detection is the most reliable method in such cases. These tests are not available at most centers and physicians can have difficulties in finding laboratories that could analyze the genetic defects because certain genes are possibly analyzed by just one laboratory. The IDdiagnostics registry has been established to provide information for physicians and other health care professionals. The database at http://bioinf.uta.fi/IDdiagnostics contains currently information for the analysis of defects in 30 ID-related genes. Another part of IDdiagnostics is a database of clinical tests. Laboratories performing these analyses, either gene or clinical tests, are asked to submit their information to the database by using a printed form or electronic submission at http://bioinf.uta.fi/cgi-bin/submit/IDClini.cgi. The clinical test database contains information about tests for clinical data, immune status, and studies of function, antibody response, cell function, enzyme assays, clinical function, and apoptosis assays. Both the services are freely available and regularly updated. The services aim at increasing the awareness of IDs and helping to obtain exact and early diagnosis.