Hi Garry – I don’t believe so. We’re on Cloverleaf 5.3 now running under AIX 5.1. From what I understood from last year’s user conference, the only AIX version common to both Cloverleaf 5.3 and Cloverleaf 5.4 is AIX 5.2. (We’re hoping to get new RS/6000 hardware in next year, which will enable us to install AIX 5.3 and Cloverleaf 5.5 without upgrading the OS and Cloverleaf versions in place on our existing production box.)