Processor layout and data distribution are important to performance-oriented parallel computation, yet high-level language support that helps programmers address these issues is often inadequate. This paper presents a trio of abstract high-level language constructs — grids, distributions, and regions — that let programmers manipulate processor layout and data distribution. Grids abstract processor sets, regions abstract index sets, and distributions abstract mappings from index sets to processor sets. Each of these is a first-class concept, supporting dynamic data reallocation and redistribution as well as dynamic manipulation of the processor set. This paper illustrates uses of these constructs in the solutions to several motivating parallel programming problems.