AbstractThe Legion Grid Portal is an interface to a Grid system. Users interact with the portal, and hence a Grid, through an intuitive interfacefrom which they can view files, submit and monitor runs, and view accounting information. The architecture of the portal is designed to accommodate multiple diverse Grid infrastructures, legacy systems, and application‐specific interfaces. The current implementation of the Legion Grid Portal is with familiar Web technologies over the Legion Grid infrastructure. The portal can be extended in a number of directions—additional support for Grid administrators, greater number of application‐specific interfaces, interoperability between Grid infrastructures, and interfaces for programming support. The portal has been in operation since February 2000 on npacinet, a worldwide Grid managed byLegion on NPACI resources. Copyright © 2002 John Wiley & Sons, Ltd.