The Caenorhabditis elegans genome contains a single dystrophin/utrophin orthologue, dys-1. Point mutations in this gene, dys-1(cx35) and dys-1(cx18), result in truncated proteins. Such mutants offer potentially valuable worm models of human Duchenne muscular dystrophy. We have used microarrays to examine genes expressed differentially between wild-type C. elegans and dys-1 mutants. We found 106 genes (115 probe sets) to be differentially expressed when the two mutants are compared to wild-type worms, 49 of which have been assigned to six functional categories. The main categories of regulated genes in C. elegans are genes encoding intracellular signalling, cell-cell communication, cell-surface, and extracellular matrix proteins; genes in these same categories have been shown by others to be differentially expressed in muscle biopsies of muscular dystrophy patients. The C. elegans model may serve as a convenient vehicle for future genetic and chemical screens to search for new drug targets.