Dataparallel C is a SIMD programming language suitable for solving many problems arising in science and engineering, We have developed compilers that translate Dataparallel C programs into C code that can be compiled and executed on multicomputers and multiprocessors. We describe the Dataparallel C programming language, the implementation of three scienti $ c programs in Dataparallel C, and the pe~ ormance of the compiled programs on three MIMD computers: the Intel iPSC/2, the nCUBE 3200, and the Sequent Symmetry S81. These case studies—an ocean circulation model, the “shallow-water” atmospheric model, and the Sharks World model-illustrate that nontrivial SIMD programs can achieve good speedup on MIMD computers and still be portable.