On behalf of Citrus Research Institute (CRIC) of Southwest University (SWU)/Chinese Academy of Agricultural Sciences (CAAS) and the Local Organizing Committee of the 20th Conference, International Organization of Citrus Virologists (IOCV), we extend warmest welcome to the scientists, associations, companies, growers and sponsors worldwide to attend the 20th IOCV conference, which will be held in Chongqing, China, from 10 - 15 of April, 2016. A post-conference tour has been also organized to visit citrus farms in Guilin from 16 - 19 of April 2016. The conference, with the theme of international cooperation and the dissemination in study and control of citrus virus and virus like diseases, will be organized by the IOCV Committee and CRIC of SWU/CAAS, with the collaboration of Chongqing Agriculture Commission and Guangxi Academy of Agricultural Sciences. The scientific programs, including plenary, sub-plenary and poster sessions will be organized by the Scientific Committee consisting of IOCV members. The mid-conference tour includes a visit to CRIC and a citrus growing area in Changshou, Chongqing to observe the tristeza, tatter leaf, exocortis and blackspot. A post-conference tour will be offered to visit well and poor managed citrus orchards with HLB and Citrus Research Institute of Guangxi in Guilin, Guangxi. We believe that the participants will enjoy to share and discuss the latest results on various theme of the research.