The Resource of Asian Primary Immunodeficiency Diseases (RAPID) is a repository of molecular alterations in primary immunodeficiency diseases (PID). It hosts information on sequence variations and expression at the mRNA and protein levels of all genes reported to be involved in PID patients. This database aims to to provide detailed information pertaining to genes and proteins involved in primary immunodeficiency diseases along with other relevant information about protein–protein interactions, mouse studies and microarray gene-expression profiles in various organs and cells of the immune system. Please note that, while available, the RAPID database is no longer being updated.