While the signal of insulin-like growth factors (IGF) in skeletal muscle cells is known to be mediated by IGF receptor (IGFR) 1, not IGFR 2, there is no report even on the expression of IGFRs during tongue myogenesis. Here we examined changes in the mRNA level of IGFR 1 and 2, in addition to IGF-I and II, during mouse tongue myogenesis between embryonic day (E) 11 and newborn by competitive reverse-transcriptase polymerase chain reaction. Immunolocalization of IGF-I, II, IGFR 1 and 2 was examined using confocal laser scanning microscope at E13, E15 and newborn stages. Immunolocalization of fast myosin heavy chain was also examined to detect differentiating myoblasts, myotubes and myofibers. IGF-I, II and IGFR 1 mRNAs were highly expressed between E13 and E15 during differentiation of myoblasts and formation of myotubes. IGF-I and II proteins were co-localized to differentiating myoblasts, myotubes and myofibers with IGFR 1 protein. High level expression of IGFR 2 mRNA was also observed between E13 and E15. However, the expression of IGFR 2 protein was sparsely observed throughout the whole tongue tissues and not restricted to the striated muscle tissue. These data suggest that IGFR 1 is related to the IGF signal transduction and the differentiation of mouse tongue striated muscle, whereas IGFR 2 is not directly involved in them.