Of late, there has been rapid development of chemotherapeutic agents for treating metastatic colorectal cancers. However, the so-called "druglag" is a long-standingproblem; it refers to the drugapproval delays in Japan that occur after drugs have been developed and approved in Europe and the USA. Clinical trials for the drugTAS -102 were stopped in the USA, but the drugwas evaluated in phase I and II clinical trials in Japan. The Phase II trial for TAS-102 in Japan provided positive results, and it received approval in Japan first, ahead of the world. Data from the global phase III RECOURSE trial were presented in the ESMO-GI 2014, where the efficacy of TAS-102 was proved again. Herein, we present data about the efficacy and side effects of TAS-102 from each clinical trial.