Japan Clinical Oncology Group (JCOG) is the largest cooperative group in Japan. The yearly accrual of 2011 was 2744 in total. Currently, there are 30 trials on accrual and 20 trials on follow-up. Those trials are supported by about 40 staffs including 5 physicians in JCOG DC/OPS. JCOG has now 15 study groups and has an established peer-review system for protocol and adverse events. There are 180 participating institutions and all roster information is managed in JCOG DC/OPS. JCOG DC/OPS issues monitoring reports for all studies twice a year. Until now, 25 JCOG studies were adopted as a reference of various cancer treatment guidelines.Current challenges in JCOG DC/OPS are as follow: (i) streamlining study process. The project for protocol development acceleration has been activated since 2009. The speed has been improved afterward and the shortest duration from concept approval to protocol approval is 173 days. Acceleration of manuscript writing is also underway. (ii) Correlative studies and biospecimen repository. Recently the demand for correlative studies is growing. We have implemented several correlative studies along with regular JCOG studies and accumulated the know-how in such type of studies. In addition, JCOG biospecimen repository has been established and specimens are to be collected under the common procedure before long. (iii) Promotion of ‘Kodo-iryo’ trials. JCOG is now planning two ‘Kodo-iryo’ trials (clinical trials using the evaluation system of investigational medical care). We are now developing a standardized procedure for conducting future ‘Kodo-iryo’ trials more smoothly. (iv) International collaborative trials. JCOG is now conducting two international collaborative studies. The harmonization of database definitions is sometimes hard and the number of staffs is not enough to handle many international trials. (v) Introduction of remote data entry system. In JCOG, all forms are still paper-based. It is mainly due to few supports by clinical research coordinator in the participating institutions. On the other hand, the yearly accrual becomes more and now we are considering introducing remote data entry system. Through all of those challenges, we aim to conduct well-designed, high-quality clinical trials rapidly and establish a large number of new standard treatments for cancer patients.