Temporal and spatial expression pattern of Xc-myc protoocogene was studied in the early development of Xenopus laevis. The myc mRNA is localized in animal hemisphere of early stage embryos. From the gastrula stage Xc-myc gene is expressed, mainly in dorsal area and the expression of the gene is maintained persistantly in neuroectoderm and epidermis. After tailbud stage, strong expression of Xc-myc gene is observed in several developing tissues and organs originated from ectoderm and mesoderm, such as central nervous system, optic cup, lens placode, otic placode, gill bud, cement gland as well as in the somite and epidermis. However no expression was observed in the endoderm at every developmental stage. Animal cap and equatorial zone of blastrulae, in addition to ectoderm and mesoderm of exogastrulae showed that the expression was occurred these areas regardless of the presence of inductive activity. These observations suggest that the expression of Xc-myc protooncogene plays important roles in the development of ectodermal and mesodermal derivatives in a specific way.