The paper proposes an XML data exchange format based on the UK AGS 4.0 data exchange format for site investigation data. The case is made for updating the existing AGS text based (CSV) format to XML. This allows opportunities for central control of versions of the data standard by reference to a centrally maintained XML schema. It also allows use of XML validation functions to ensure files conform to the agreed standard. Data structures and stylesheets have been developed for borehole data and field testing data. A simple structure was adopted that can be used for importing data into a spreadsheet if required.