Non-receptor type of protein-tyrosine kinase Syk(spleen tyrosine kinase) was isolated in the University of Fukui in 1991. Syk is ㎞own to beessential for the various physiological functions, especially in hematopoietic ineage cells. Moreover, ectopic expression of Syk by epigenetic changes is reported to cause etinoblastoma. Recently, novel Syk inhibitors were developed and its usefulness has been evaluated in thetreatment of allergi crhinitis, rheumatoid arthritis, and idiopathic thrombocytopenic purpura. In this review, we will summarize the history, structure, and function of Syk, and then describe the novel Syk inhibitors and their current status, Furthermore, we will introduce our findings of the adap-tor protein 3BP2(c-Abl SH3 domain-binding protein-2), as a novel target of Syk.