Protein-tyrosine phosphorylation catalyzed by protein-tyrosine kinases (PTKs) is well recognized as a key regulatory event in a variety of biosignal transduction events such as growth, differentiation, maturation, programmed cell death, and malignant tumorigenesis. Recently, it also becomes evident that PTKs may play an important role in developmental fertilization, and early embryogenesis. In particular, studies on frog, Xenopus laevis, have witnessed to the general importance of PTKs in regulating these developmental events in amphibian species, Earlier studies have shown that a group of protein serine/threonine kinases and some cellular components other than PTKs act in maintaining and driving cell cycle events. In this review, we will summarize recent progress in understanding that a number of PTKs of both receptor and non-receptor (in particular, Src-family) type are present and  play an important physiological role in Xenopus.