Clusters of workstations are a popular alternative to integrated parallel systems designed and built by a vendor. Besides their huge cumulative processing power, they also provide a large data storage capacity which allows efficient implementations of large-scale applications which are I/O intensive. This paper proposes a language, compiler and runtime software solution to the problem of parallel I/O on clusters. The proposal is presented in the context of High Performance Fortran and its compilation and run-time environment that is being developed at the University of Vienna. The system provides efficient support for explicit I/O operations on parallel files, accesses to sections of multi-dimensional arrays stored in parallel files, checkpoint/restart operations, and time step output and input operations. The paper also presents experimental performance results using the implementation of the developed software on a Beowulf-class cluster system.