Several genes encoding transcription factors with a helix-loop-helix (HLH) motif are involved in the early process of neural development in Drosophila spp. We report the isolation from the rat a homolog of one of these genes, called hairy. The rat-hairy-like (RHL) gene is expressed early during embryogenesis. In contrast to the restricted expression of hairy mRNA in Drosophila spp., however, the mRNA encoded by RHL is detectable in all tissues examined. Stimulation of PC12 pheochromocytoma cells by nerve growth factor, basis fibroblast growth factor, or epidermal growth factor or of Rat-1 fibroblasts by epidermal growth factor causes a rapid and transient induction of the RHL gene. Thus, RHL acts as an immediate-early gene that can potentially transduce growth factor signals during the development of the mammalian embryo.