We have isolated a full-length cDNA encoding Xenopus L-arginine:glycine amidinotransferase (XAT), which shares a highly conserved sequence with human, chick and rat amidinotransferase. Although there are some studies about its structure and function in energy metabolism of adult tissues in some other species, little is known about its roles during early embryonic development. Characterization of embryonic expression indicates that XAT is differentially expressed around the yolk plug including the dorsal blastopore area at early gastrula stages and is extensively expressed in the midline of the neural plate of early neurula stages. Sections reveal that its transcripts are located in the notochord. In the tailbud stage signals are found both in the notochord and trunk area, whereas only faint signals can be found in the cephalic part.