SR Buffer is a mixture of nutrients and designed to reduce serum in culture medium for cell proliferation. It is suitable for general basal media (e.g. MEM, DMEM, and RPMI-1640) and complex media (e.g. Ham’s F-12 or DMEM/F12). The usage of SR Buffer is convenient and easy. We recommend mixing SR Buffer with fetal bovine serum (FBS) in ratio of 8 to 2. The mixture could be considered as serum replacement in culture medium. When cells are cultured within medium contained SR Buffer/FBS mixture, proliferation is reported to be similar to those which are in medium supplemented with serum. Application of SR Buffer could reduce serum in culture.