GPX is an environment for the storage and retrieval of raw and processed MIAME compliant microarray experiments. The system has been developed at the Scottish Centre for Genomic Technology and Informatics (GTI). GPX has a web accessible front end, GPX Discovery, that enables querying and retrieval of biochip data and experimental information based on various search criteria. GPX Discovery also enables the comparison of microarray platforms using the BioLink MatchMaker interface. GPX has been in use since 2003 to provide online access to raw, processed and meta microarray data analysing gene content, expression protein levels in the fields of immunity, oncology, infection and is part of the Edinburgh National Translational Cancer Research Network Centre resources.